Ukraine is modifying a large variety of smaller aircraft to be suicide drones. Yes, A-22s/A-33s are used which cruise at like 100-120MPH or so (though there's been some talk of turboprop conversions of the same, too). But other small civilian aircraft which cruise at more like 160MPH have been employed, versus a late approach speed of the Embraer of 180-190MPH or so.

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).