Yes.
Here is an example of lactate and HR curves shifting over several training blocks:
Short version (I took notes):
- Test1: Sept 11, 2022
- Test2: Nov 9, 2022
- Test3: Jan 21, 2023
- 20 weeks from test1 to test3
- Average of 10 hours/week
- Intensity Distribution: 77% z1/z2 (59% zone1); 20% z3/z4; 3% z5+
Yes 59% zone1 - what some still call junk miles.
The lesson here is that if you come out of an off-season, and have productive base training, then reduced HR at a given power CAN BE (and likely is if your HR is well behaved) a signal of improving fitness. And a signal to adjust training and/or do an FTP test.