Originally Posted by
El Bunto
Erm, FR24 and other trackers don't squint up at the overflying aircraft and try to guess the variant; they look the ADS-B or Mode-S emitted ICAOhex up against a database of aircraft. It's not possible to mix a 737-8 and a 737-800 up unless the FAA, CAA etc has already done so in their national registry.
I haven't noticed any such instances on FR24, but other flight trackers (RadarBox24, for example) have certainly been known to get confused between a Max and an NG.