So "technically" that's not what they are doing. Redhat will happily give any of their customers the source to any GPL binary that customer received from Redhat. This does satisfy the GPL license requirements. Redhat will then immediately terminate their contractual relationship with that customer (i.e. we owe you no more binaries and therefore no more sources AFTER today) if that customer does indeed re-distribute that SRPM.
In other words they are not imposing any restrictions on this specific GPL binary/source pair. They are just ending their contract with you and cutting you off from all future redhat binaries AND sources.
I believe this is a bullshit end-run around the GPL, but whether this intersection of contract law and copyright law actually represents a "restriction" as defined in the GPL is going to 100% be up to a court to decide.