Follow-up: Why doesn't the Forerunner 570 get Real-Time Stamina if the hardware is basically the same as the 970?

A few days ago I asked here whether the Forerunner 570 has Real-Time Stamina, and the answer was clear: it doesn't. It's only on the 955, 965, and 970. Thanks to everyone who replied.

Now I'm asking a different question, more out of curiosity than frustration. Real-Time Stamina is a Firstbeat algorithm, not a sensor. As far as I understand, it's derived from heart rate, pace/power, and your training history (VO2 max, lactate threshold, HR zones). The 570 has the same Elevate Gen 5 optical HR sensor as the 970, supports HRV status, training readiness, training status, and can broadcast/pair with external HR straps and power meters. The main hardware differences I'm aware of are ECG, the flashlight, the skin temperature sensor, and the sapphire/titanium build, none of which feed into stamina.

So, is there any technical reason the 570 can't run Real-Time Stamina, or is this purely product segmentation to keep a gap between the 5xx and 9xx lines? I'd also be interested to know if anyone has seen Garmin add a previously tier-locked software feature to a lower model via firmware, or if that basically never happens.

Not trying to start a rant thread, I just find it odd that the 570 gets things like the speaker, mic, and ECG-grade HR sensor but not a purely software metric that older watches like the 955 already have.