I've wondered about this. To what extend does a Nest drive the CV system? For example does it do modulation? If so, does is use OpenTherm - and thus only works

I've wondered about this. To what extend does a Nest drive the CV system? For example does it do modulation? If so, does is use OpenTherm - and thus only works on new CV systems? If not, how is it not 10 (OK, 5) years behind?