I don’t know if you can technically consider + addressing aliases. Many spam bots and data harvesters strip them out anyways, effectively removing that email quirk for obfuscation uses.
At any rate, support for plus addressing and catch-all addresses are two different things. The former, I believe, is an email standard. The latter is implemented on a per host basis. Some dont allow/discourage it for spam reasons.
But as you point out, catch all handling is incredibly useful for moving between mail hosts.
Let us know what you find out!