[starfezzy]

The absolute value does matter for several reasons, but the obvious one that sticks out is in understanding the effectiveness of your training.

Example: if your real max is 60, but your watch says 50, you may be wondering why hard training isn’t increasing it.

Another example: if your real max is 35 but your watch says 45, you may misinterpret the signal when it jumps to 55 relatively quickly after a few weeks of hard-ish work.

Plus, if the value is significantly inaccurate then who knows what else is inaccurate about it? I appreciate that Apple have put effort into making it accurate.

[matsemann]

But my point was more that if it shows 45 (but real is 35), and then you work out a lot and it shows 55 (but real is now around 45), it's still useful even though the values are off. As long as the error/bias is the same.