Booboo we're talking about his ability to react to Ftg. His reflexes allowed him to do this successfully. Therefore, That point holds. Also, he did this twice, not once.
Incorrect, Gai was able to combat the phasing of Kamui to an extent. His hand speed prevented Obito from touching him, which is important enough. The only thing base Gai failed to do was create an opening to land a strike of his own.
You react to the strike, not FTG. I wish people would get this right, such common knowledge, yet people are still foolishly saying this. The teleport itself, no one has ever intercepted or reacted to ftg. The attack that comes after has though. Minato didn't attack after he teleported to Bee, so there was nothing for bee to actually counter react to. It's called anitcipation, not to mention you never saw if Bee noticed the mark on his tentacle, nor did you see when Bee placed his sword behind him, if it was before minato teleported, then thats called anticipation. The other time bee "reacted", again was off panel, did you see when he brought put his tentacle? No. Not to mention Minato wasn't fighting Bee, or even looking at him, he was focused on Ay. So not relevant.
Guy knew it was useless to go in with big moves against Obito, he said it himself. Would've been useless for him, hence why he went with his nunchucks in base. He would've never landed a strike, it was 4 vs 1, if he could land a strike, they wouldn't have needed kakashis kamui.
You're trying to use Bee as a means to justify Itachi reacting to ftg in cqc (which wasn't even a battle of killing intent situation), yet not once have you addressed how he deals with multiple ftg opponents. Obito, Izuna all fell prey to FTG in little time. You telling me Itachi won't falter once against ftg lol. He's not better than Tobi in cqc, he's not a sensor, he has poor stamina, and he doesn't have eyes in the back of his head. Tobirama wrecks him from all sides.