Because of the way the bash ebuild/autogen is designed, it uses an external readline, and attempts to use the version that was bundled with bash.

I have masked readline-8.2 since it needs some work and testing, but bash 5.2 is bundled with it. Thus bash-5.2 can't merge in next-release.

I think it's best to de-couple the readline ebuild from the bash ebuild so that there isn't this very tight inter-dependency between bash and readline versions. They are not autogenned together so we have no assurance that we will have an acceptable version of readline for bash.