That is quite a serious bug, Remy.
Talking about "bugs" seems a bit extreme to me.
We could talk about a proposal for improvement, which is more appropriate to the situation.
Indy has been like this since TLS support existed and it is for compatibility with the past that it is better to stay that way.
Changes like this should be made with new versions.
For error messages, I do not agree with "simplifying" them because now they give exactly the precise point on what is wrong.
Maybe they are a bit "technical", but honestly I prefer a precise technical message than a generic message that does not lead me anywhere.
I agree that not everyone is a specialist in security protocols, but in any case it is being implemented and therefore a minimum of knowledge must be put into play, we are programmers not end users.