The reason that happened to Blackwell was partly because Jnr wasn't capable of knocking him out. If a toddler punched you in the head for half an hour the same thing would happen.
He is entertaining and gifted but hasn't shown much to suggest he could beat someone classy who has a gameplan.
Agree with all your thoughts but I can imagine a logic in waiting until GGG ages more before taking him on.
From what I heard, kind of one step removed, Booth wasn't perturbed by one thing in sparring, as they would have it, but rather by a combination of factors including Snr's interference...