No, that’s not likely. I don’t think our server setup even makes it possible to have different configuration per account.
It’s more likely that I wrote that announcement based on the release notes of PHP themselves and didn’t consider that our builds might not have all of those things.
I can ask and see if Argon2 can be added. But given that you’re the first to ask for it, consider that the answer may be “no, just use bcrypt or upgrade”.