PTFE is newer than my sewing days. The logic used to be that if you were sewing Dacron or nylon (tents, awnings, sails) you had a choice of Dacron thread, cotton thread, or "dacot" which is a Dacron core
wrapped in cotton. Dacot was the best choice, because plain Dacron thread could saw through the cloth, plain cotton thread would rot
out, and dacot would take longer to rot
out--but not harm the cloth.
If you've ever looked up at an old sail and seen the enlarged holes around every stitch of the thread, that's what Dacron thread does to fabric
. It enlarges the holes and makes a 'dotted line' encouraging failure. Where a weaker thread (cotton or dacot) would fail first, allowing the cloth to be simply restitched for a longer life.
I have no idea how PTFE fits in there but suspect a lot would depend on how much it has been stretched, etc. before being made into a finished thread. Anyone familiar with those aspects of PTFE?