Can’t speak to the first point, as it could be for several reasons as outlined above.
On the second point, if your fractional utilization (FTP as % vo2max) increases, then your LTHR - or HR at FTP - will also increase.
So if “171 for an hour” was roughly around FTP, and last year it was 166bpm, then it’s possible your fractional utilization increased (say from doing a lot of SS or threshold work).
Or it’s something else.