How are you setting HR zones? This is what I use:
And as you can see zone 4 is 11 beats below FTHR up to FTHR (depending on FTHR since it’s a percentage).
And this is how mine looked after Baird + 6, which is 5 x 1.5 min, so the HR will get higher for each set, but even then, just look at the distribution (the + 6 has 30 min zone 2 at the end, so I spend a good deal more time in zone 2):
So for Baird + 1 your HR data looks like it fits, but your zone doesn’t.