To what extent is lactate tied to heart rate?

A lab test late last year gave me Aet at 200W (1.86mom/L) and 140 BPM; AnT at 250W (3.97mol/L) and 160 BPM .

RPE and breathing both seem unaltered with respect to HR since then but power is now 230W at 140 BPM. I don’t have data at 160 BPM over a long enough time-scale to be meaningful but FWIW last week’s 4 x 8 session gave 290W at around 160 BPM (which in itself suggests my FTP is set a shade low, at least if the 2 x 8 FTP test protocol is to be trusted). 260W comes in at 150 BPM; 200W now comes in at 120 BPM and my long Z2 endurance pace—175W—is now 110 BPM for the first 90 mins; thereafter a gentle rise sets in with 130 BPM at around 5 hours. These data all indoors with comparable environmental conditions (nutrition; hydration; sleep status; etc.).

Is it fair to presume that AeT power is now 230W? If so should I be doing Z2 long rides at 200W? I gather that ISM has his riders target ‘upper’ Z2; does this imply that you can go too easy even in Z2?

Any thoughts on the above greatly appreciated. (BTW I had a read of the LT1 thread from a couple of years ago but it raised rather more questions for me than it answered)