This may well be a good thing

It seems Proton was the main driving factor for pledging for GCM mode which in turn required a lot of changes to the protocol to mitigate its brittleness. The reason is that the major web browsers still do not implement the faster OCB mode and it had to be implemnted in JS for that reason (cf. non-availability of SRV record queries). This is the major "chism" - I explained over at https://libregpg.org that proliferation of algorithms is a bad for security and that OpenPGP tried to avoid that as much as possible.

BTW, One good thing with the delays is that meanwhile Rogaway's patent on OCB expired and there is zero reason not to use OCB. FWIW, there has even always been a royalty free license for almost all software implementing OCB.

That should have been clarified in the article. This is a different usecase than normal PGP use.
Now proton is sitting on million of keys which are only protected by password that can be subject to various bruteforce attack. The security is much lower than what PGP provides.

Note: I believe that SRP is actually Secure Remote Password, because it proves possession of the shared authenticator using a challenge-response instead of encrypted direct transmission (e.g. TLS)