That's why 1 Bitcoin is not 1 Bitcoin, because price matters. This phrase is being thrown in bear market to cope with a price loss, but in reality everyone is looking at the price of Bitcoi against USD and base their decisions on that. No one is going to set price in BTC for their goods and services and ignore the change of Bitcoin's value. Even signature campaigns that for years maintained a flat rate had to eventually adjust it when the price became too high.
Thank you for speaking the truth, which I believe many people also understand, but they deliberately don't believe it to be true, bitcoin will never get rid of its dependence on fiat. The saying "1BTC is 1BTC" is just a saying to comfort us through this fierce bear season, that doesn't mean bitcoin doesn't need fiat or its value never will change. I find it funny when many people say 1BTC = 1BTC, but meanwhile they wait for bitcoin to drop in price to buy them instead of buying at high prices, and they say they don't care about the USD value of bitcoin.
If I'm getting you right, I think you are saying it wrongly. 1btc is 1btc, and nothing would change it except the people who wish to amend product prices to suit the current evaluation of 1btc. It's like saying; 100 dollars is no longer 100 dollars because it can't buy as many groceries as it did years back. These are just market changes that have no meaning to the status of the currency. If one bitcoin is worth 60k today, you won't expect 1btc not to purchase a product of 60k because 1btc was 16k yesterday. That is why product managers, including the signature managers would have to adjust the price according to the worth. Yet it doesn't change the fact that 1btc = 1btc. People only get confused about this, as everyone is here to make profits out of the volatile nature of bitcoin, which is pegged to the dollar for easy market evaluation. If bitcoin was not pegged to fiat, it would have been a hell of difficulty to make trades, as nobody would be able to understand the bear market and bull market, it would have no volatility in dollar price too, but on product price; in a world where only bitcoin is accepted. How then will people know the actual worth of bitcoin when they want to purchase it with cash? wouldn't it be difficult to determine using products as a determinant? So, Fiat, indeed, is crucial to the existence of bitcoin in determining the worth of 1btc to the market.