Can a periodontist usually determine whether there is a need for an upper molar area sinus lift?

Yes: Yes. My guess is that you need a dentist whom you have confidence in and haven't found one yet. You will be better served by finding one than looking for answers on the internet.

Yes: The periodontist i work with makes this determination, performs the procedure, and places the implant body. This, i understand to be common among periodontist today.

Definitely: Periodontists that placing dental implants. These specialists have the expertise to diagnose sinus lift procedure according to the cone beam ct.