Stredda
Runs naked through virgin scrub
I have found that commuting to work is great for zone 2 base fitness.Those coaches and scientists you are listening to are talking about Z2 as part of a structured training which probably sets out a 7 days a week program, every week, not a casual 20-30km ride.
If you are only doing 1 ride a week, you will get far more benefit in every way doing a MTB ride on trails with hills than rolling in Z2 on tarmac or gravel.
We ride for fun, so do what makes you happy