The reasoning behind the P2PK ban makes sense (IMHO) once you realise that it's about "permanent UTXO set bloat" rather than "total bytes pushed on-chain."
Then, why P2TR or P2WSH is not banned as well? If you compare compressed P2PK, then it is one byte more, than in P2TR. And when it comes to P2PK, then it is always spent by a single DER signature, while P2TR can push a lot of data through TapScript.
So, if someone wants to use fake public keys in P2PK, then that person could simply use P2TR or P2WSH, and get it one byte cheaper. And, as you can see in practice, it doesn't really matter for spammers, if they consume one byte more, or one byte less, because existing spam usually allocates more coins than needed in advance, and there is some change, which is usually sufficient to post the same spam again. And because the price of BIP-110 coin is much lower than non-BIP-110 ones, then it is actually cheaper, to use even very inefficient methods.
Also, it is funny to see, that they consider Satoshi's early transactions to be incompatible with BIP-110. Was Satoshi a spammer? It only shows, that they cannot create a good rules, which would filter the actual spam, without affecting real payments in any way.
I can see no reason to block P2PK, when it actually leads to less bytes pushed on-chain in some scenarios. And if blocking P2PK would really work, then spammers would simply switch to other address types, for example P2TR or P2WSH, and would achieve the same UTXO pollution, while also wasting one byte less per UTXO. So, blocking P2PK actually affects mainly some early adopters, who may need to use P2PK for that reason, or another, while leaving actual spammers completely unaffected, because they have a lot of options to choose from.
a P2PK output could conceivably be spent, so its data must be kept in the UTXO set permanently
Switching to storing data in private keys, and revealing them through weak signatures, solves that problem completely. And it already happened in practice, for example:
https://web.archive.org/web/20251108213635/https://www.bitmex.com/blog/the-unstoppable-jpg-in-private-keysUnder this criterion I think banning P2PK but allowing the equivalent multisig trick makes no sense though...
Don't worry, they plan to block 1-of-15 multisig:
https://github.com/bitcoinknots/bitcoin/pull/422However, if for example 2-of-3 or 15-of-15 multisig will be unaffected, then guess what: weak signatures will still allow pushing the same data. And even if the cost of doing so will be bigger, low price per coin will still make it doable, and probably still cheaper, than on a non-BIP-110 chain.