Richie,
I agree, that if you get the plywood down on the frame fairly quickly, with plenty of first-rate construction adhesive underneath, and screw it down tight every 8 inches, you probably don't need to worry about priming it. But, if a hump or a curl is big enough, it is really hard to do, especially if it is 3/4 inch plywood. And, if you lay a humped or curled sheet down on the adhesive covered framework, and then have to flatten it out as you go, then that pushes and squeezes the adhesive out everywhere.
Back in the old days, when I was using this method to put down plywood flooring on joists, I just made my wife sit in the middle of the sheet until I was done.
Course today, that would be called "spousal abuse"! (Just cuz she got woozy from the fumes now and then.)
Priming the plywood quickly lets you take your time in completing the table.
Mannyrock
