Hmmm.
Thanks for the link. But that says:
Correct icon is set based on the ICAO Type code. When correct ICAO Type code has been provided, the icon will be correct.
which is clearly not the case - Boultbee don't need to tell FR24 that G-IRTY is a Spitfire, or that its ICAO designator is SPIT. FR24 already knows that:
Heck, they even show a photo of it looking not very much like a twin-jet airliner !