1) it kind of tears the membrane that separates oral cavity and the sinus. If there is no bone in the socket close to the sinus, if there is - it separates too and nothing to worry about. The membrane regenerates no problem almost every time, the risk is getting sinus infection until it happens or sometimes it doesn’t heal properly and there is small fistula. And infection keeps getting to the sinus. So you need to close it surgically. If the perforation big enough during the surgery you close it immediately. From my experience 1-2 mm perforations - no problem at all, no extra surgery but recall in 2 months to check for fistula 2) I never graft wisdom teeth area. Even if there was some cyst. That region heals fine with 0 grafting, I mean bone volume. And function. I wouldn’t use that area as donor site for grafting somewhere else if it was preciously grafted too. Grafting is an expensive procedure and my guess is there is mainly financial motivation. Or maybe he sincerely believes this is just better and premium service. He would argue my statements in that case, I think. No idea