Some Guy wrote:

Look what the original poster (OP) said:

"Currently I'm busy fastening 3/4" plyboard over the ceiling
rafters (so objects to be stored won't crash thru the drywall
ceiling)."

So we can assume that the rafters are strong enough to support someone
wiggling around putting plywood down?

3/4 plywood to tie the rafters together will certainly give some
additional strength to the load-bearing capacity.

It's adding a substantial load just sitting there and it's overkill.
It will help spread out load, it won't add to the overall capacity.

R