TBH, I don't really understand the details nor the implications of that information.
I would expect the system to have some communication in place like this:
1) Apt: Server, hand me your data.
2) Server: I will give you this mirror; get your data there.
3) Apt: Ok.
4) Apt: Mirror server, please hand me your data.
5) Mirror server: ...
6) [apt: hmm.. mirror is no available.]
7) Apt: Server, mirror is not available, please give me another mirror. ( ← This is important. )
8) Server: Here is another mirror.
9) Server: (Marks mirror server as 'possibly down' and checks connectivity again.)
As far as I understand your comment, apt cannot ask the server for a different mirror(?)
I guess in that case, this discussion would be better suited in the apt bugtracker, I guess.
TBH, I don't really understand the details nor the implications of that information.
I would expect the system to have some communication in place like this:
1) Apt: Server, hand me your data.
2) Server: I will give you this mirror; get your data there.
3) Apt: Ok.
4) Apt: Mirror server, please hand me your data.
5) Mirror server: ...
6) [apt: hmm.. mirror is no available.]
7) Apt: Server, mirror is not available, please give me another mirror. ( ← This is important. )
8) Server: Here is another mirror.
9) Server: (Marks mirror server as 'possibly down' and checks connectivity again.)
As far as I understand your comment, apt cannot ask the server for a different mirror(?)
I guess in that case, this discussion would be better suited in the apt bugtracker, I guess.