We discussed this on my wolfcraft pocket hole jig review as this came with countersink screws, one suggestion was to put a washer around the countersunk screw. Not tried it can't vouch for strength compared to correct pocket hole screw but in an emergency may be an idea.
Would be nice if someone had the correct equipment, for them to do a little experiment to see how significant the difference in strength is between countersunk, countersunk with washer and pocket hole.