How heavily does Apple Watch rely on bike power meters?

Can anyone help me understand how heavily Apple Watch will rely on a bike power meter when one is present, especially in active calorie calculations?

I regularly ride an e-bike -- so I'm doing a lot of work, but the bike is doing work too --, and Apple Watch massively over-attributes calories burned while cycling. I would *like* to keep tracking my workouts in Apple Health (especially including calories burned), but the terrible Apple Watch e-bike algorithm is wreaking havoc on data quality -- e.g., it often doubles or triples the true calorie expenditure (as computed using the e-bike's built-in power meter).

I know Apple Watch is capable of using an external power meter -- I do this with my non-e-bike --, but I don't know how heavily it weights it in its calculations. Maddeningly, there does not appear to be a way to pair the e-bike's power meter with the apple watch (no bluetooth), but I could buy an add-on pedal power meter... I might be willing to if this meant that Apple Watch's calculations would magically become accurate, but is there any way to know before spending a ton on this whether it might work? Any guidance on the algorithm?

Thanks!