I like doing this, an is one of the reasons that I use the Zwift workout player, it’s a click on the companion app and with the play controllers, once selected once as the menu’s keep positional memory press up on the left and a on the right to toggle, so don’t even need to lift off the bars
I would say that doing it automatically would be a bit jarring, i tend to come out the interval, slow my cadence and then switch it
This has been a long standing request, going back to 2019 if you search “toggle erg”, so I don’t see it happening
