I think this may be at least partially the case. I switched off the schedule over a week ago and its not tracked my temperature since then (it also didn't do it the couple of days BEFORE I switched it off either.
But I think it maybe HSA to use a schedule for it to stand any chance of tracking the temperature. Which is strange and annoying, because the "normal" sleep tracking works irrespective of whether a schedule is used - so EVERY night I wear my watch I get the tracking for hours in Deep, REM, sleep etc, breathing rates during sleep etc. But the temperature tracking rarely works.
I've still not had any definitive answer from the case I raised- it is still open. But I'm starting to feel that this is maybe a hardware issue.
The main selling point for this feature was for women to use it as a tool for ovulation tracking assistance. Is anyone following this thread trying to use it for that? I'm male, so for me I am using it just because its (meant to be) there. But does it work better for female users using it for the main intended purpose I wonder? If it works only occasionally at best for female users in that scenario then I would be a lot more bothered by this!