Where those screw points are exposed, you could screw on small pieces of plastic tubing.

Except for the hardwood dimensions, I have an identical problem.  5/8" subfloor, 19/32 underlayment.  I could not find 1-1/4" subfloor screws that were collated for a senco gun.  So I am going with 1-1/2".  I hate the idea of having 1/4" of exposed screw points sticking into my unfinished basement where I may be doing some work and scrape up my hands (or future home owner's hands).  However, with this method - the subfloor will have full-diameter screw shaft all the way through it rather only holding the tapered end of the screw.  It will be a more solid connection, hopefully a better floor overall.

I gotta buy some screws for my Senco. Project is to secure 5/8 plywood underlayment over 5/8 plywood subfloor. Was planning to use 1.5" screws (08F150Y). Want them to have a good grip to subfloor. But these are fully threaded. Wondering now if partial threaded is better for this application. But the partial threaded are 1 3/4" (08F175Y) and I am concerned that when countersunk that not enough thread will be in the subfloor.

Senco screws for 5/8 plywood underlayment over 5/8 plywood subfloor