A regional jet on approach and a prop aircraft in cruise don't necessarily look that different in ground speeds, altitudes, or even radar cross section to most radars.
This is the Russia war coming home to roost. They better admit that they are engaged in an actual war, and stop allowing civilian aircraft in areas that are attacked frequently.
ADS-B is an augmentation of that, which makes receivers simpler, but ATC generally does not rely on it exclusively (except in some very remote regions), nor on any type of active/cooperative signal or response – if everything else fails (maliciously or accidentally), there's usually primary radar as well.
And remember, radars vary groundspeed, which can easily vary by +/- 25MPH from actual (and will be reading the Embraer's speed on the low side).