Thanks to everyone who commented and I apologise for the delay in replying.

So it seems that complete clarity is not yet available. Ok.

A couple more questions in the search for clarity:-

1) Can anyone confirm or deny that Red Hat places contractual
limitations on what a subscriber (who has access to the RHEL7 SRPMs) can
do with the source code so obtained? Yes, I know this has been discussed
but I don't think it has been explicitly confirmed. One must infer that
there are contractual limitations (otherwise why remove public access to
SRPMs) but it would be nice to be absolutely clear.

2) This is a legal question but it is relevant: If Red Hat uses a
contract with its customers to prevent a customer who is a recipient of
the GPLd source code (when received via SRPM) from redistributing it or
rebuilding it as they please, wouldn't this mean that Red Hat itself was
in breach of the GPL licence conditions?