I don’t think that’s the case, purely because they haven’t already added the Nest Protect to Google Home and show no signs of doing so. It seems to me that they’ve left the Nest Protect entirely untouched.
There’s a trick to use the Home/Away status in openHAB: use a Google Assistant routine to toggle an openHAB item, which can then run an OH rule. It’s not instantaneous, but the change is picked up within a minute or so (Google home geofence example).
It’s been long enough that I see no reason to expect to expect anything to change. Personally I’m not too bothered by it, because the Nest Protect is (in my opinion) the best smoke detector available. It’d be nice if it integrated with openHAB, but I don’t feel like I’ll gain that much from doing so. And with any other smoke detector, I’d lose features like the built-in notifications (via the Nest app), the nightlight, the “I’m about to sound the alarm” warnings, and the reminders to test it periodically.
It might actually be a good thing that Google hasn’t messed around with the Protect, because the odds are that they’d just make it worse. 