OK, I’ll bite
... It’s not like they’re cheating you or anything
If the sensor only has 14-bit dynamic range, it only needs a 14-bit ADC. The 6200 is IIRC the first CMOS sensor to come near astro consumers that has the full well depth large enough and with sufficiently low read noise to effectively utilise a 16-bit ADC, even then, it doesn’t absolutely need it. On other sensors, this subtle mystical resolution from a 16-bit ADC of which you speak would just be lost in the noise.
Any rounding “errors” in the data are taken care of during stacking == averaging.
My take on it is not to drop the gain beyond the peak DR sweet spot, as that’s where posterisation/quantisation errors can creep in.