You should visit a country with hyperinflation and you will get your answer.
Imagine in Venezuela you want to price something in bolivar, it can be worth a certain amount today and another higher amount tomorrow. Nobody sells their product at a "fixed price" in Venezuela simply because their currency value is volatile, in this case declining. One could use a more "stable" currency like USD to price everything and give a variable value in VES but that also doesn't mean bolivar is priced in US dollars and can only be purchased by it!

It is the same with bitcoin, since its price is volatile (in this case rising most of the times) people use another more common currency to set the price specially since they already use that currency. For example in Japan the shop would set the price in JPY and you pay a variable amount of bitcoin depending on the price at that time.

In other words 1BTC=1BTC does not also mean 1BTC=1product.

Hats off to merchants who uses bitcoin valuation but we aren't at that stage yet where goods and services are priced in BTC and not in fiat. I do not even know if that time will ever come. Most people still prefer convenience over techs that they might find complicated.

Items are priced in U.S. dollars and paid in Bitcoin, but commodity prices can still fluctuate. If the price range of the US dollar is not very large, it should be possible to use the US dollar as the benchmark first.

Currently, Bitcoin pricing is more difficult to achieve because of too much volatility.

It is not. You probably think it is difficult because you have never been accepting bitcoin payments or making any payments yourself. The large number of merchants who have been dealing with bitcoin payments for years suggest it is not as difficult as you think.
All you need is an API to fetch the price and a simple arithmetic to convert the value of the goods to bitcoin based on that price. There are even third party "payment processors" that receive the bitcoin instead and pay you the fiat equivalent.

At least in this point, don't listen to the bitcoin puritans. They will always say 1 btc is equal to 1 btc. But that's not practical for the time being. Because bitcoin's value fluctuates greatly within a short period of time which makes it unsuitable for pricing. So from a business perspective, it makes sense to add a USD/local currency equivalent and let the pricing in bitcoin fluctuate in accordance to that.

Practically you can't have a single pricing of a product in bitcoin. It wouldn't make sense to the buyers. If it changes as per the USD equivalent, then it makes sense!

If a product is priced in Bitcoin and USD at the same time, it is a very troublesome thing for merchants.

You said Tesla can pay in Bitcoin, but only accepts Bitcoin.They will not disregard normal market prices and will not disrupt normal market order.

For me personally, when Bitcoin is falling, I will consider accepting Bitcoin payments, simply increasing the number of my holdings, but the price of Bitcoin is very volatile and I will continue to change.

Generally speaking, when Bitcoin has not become a universal payment system in the world, the pricing of commodities is still based on legal tender. In many underdeveloped countries where economic crises have erupted, everyone’s choice is still the US dollar.

We don't have to and it depends on our needs, especially regarding the efficiency of tax reporting. As far as I know, there are no countries that allow bitcoin to charge ownership or transaction taxes based on the number of bitcoins, but the value in fiat in the local country.

Maybe we can, we can implement it like NFT item pricing. The more "valuable" the attribute of the item is, then we can call it a special edition and set a different price from the others. For example, a pair of underpants with Satoshi's signature that can only purchased for 1 BTC.

Which means to say, for as long as Bitcoin has a price value in terms of fiat and fiat itself remains the default currency, Bitcoin's equivalent to fiat will always be taken into consideration. It would only lose its relevance when fiat becomes the obsolete currency nobody would accept anymore. Otherwise, the argument that 1BTC=1BTC is no match to 1BTC=$20,000 turning into 1BTC=$70,000 or 1BTC=$10,000. You may price your house fixed at 1BTC but whether it will sell or not will highly be influenced by Bitcoin's fiat equivalent.

Merchants should be able to adjust it right? Idk much about tech stuff but since some merchants are able to accept Bitcoin as payment, the barrier of volatility shouldn't be much of an issue (though the discrepancies at times is still a problem, albeit small in effect I think). 1BTC = 1BTC would always hold true, but pricing a product in terms of BTC shouldn't always be a constant value, BTC itself is a volatile market, changes would naturally occur to the price hence why the value of BTC to be paid should also be adjusted. We use fiat to convert and calculate it because it's a lot easier for both sides.

Pretty much why I say that Bitcoin wouldn't really be separated from fiat anytime sooner imo. We can't just slap into the world that they should price everything into Bitcoin, without any corresponding currency to help them actually provide a solid value to products since BTC changes in value, products don't.