Note that for main wiki initialization we do have ApplicationReadyEvent. The issue might still be true, it needs to be tested when initializing a wiki from a domain to see if a WikiReadyEvent is triggered then for main wiki or not.
Discussion with Thomas on the subject: https://matrix.to/#/!ikPtGZaGWtyblizzlR:matrix.xwiki.com/$1706175875198TyQZc:matrix.xwiki.com?via=matrix.org&via=matrix.xwiki.com&via=helsinki-systems.de