There can't be "over rating" in tube power amps. It's not dependent from the ohms of the cab or anything also. A power tube can put out what it's specs show.
The only "reason" to make you think it's less than 100 watts, is, lower plate voltage by design, under designed (for the circuit) output transformer.
Or, it sometimes is relevant to the guitar frequencies in general...if the carvin is more hi-fi as pointed it'll seem less "loud" by not pushing mids and pushing more bass (rolled-off in many amps) frequencies.
Vai uses TS-100 (one or two) for his 4x12 stereo on stage cabs.