A little aware of capabilities of both types, I don't think mistaking
Fishbed with Fitter would have "no impact" on the troops. Fighter
capabilities of Su-17 are poor, but MiG-21 cannot haul heavy air-to-
ground ordnance (like H-29 missile) or a nuclear bomb, though I don't
remember if the latter capability was well-advertised in the Warsaw
Pact forces...

Best regards,
Jacek

On the other hand, mistaking one type of hostile
aircraft (a Su-17 Fitter) for another type of hostile aircraft (a
MiG-21 Fishbed) would generally have "no impact" -- except "if
friendly countries were flying some aircraft types that are normally
considered hostile."