hi and lo, that's more often true than false. But sometimes one microphone in a pair has been damaged or has deteriorated and perhaps the owner doesn't realize it. In that case a repair can improve the match between that pair of microphones at least somewhat.
With professional-quality condenser microphones of any given make and model, capsules vary more than amplifiers. Also, performance-altering damage happens to capsules far more often than it happens to amplifiers. This is why, for example, Schoeps sells matched pairs of capsules, but they don't match amplifiers; those come out so similar that there's no real need (but see below re: matching capsule sensitivity and amplifier gain).
The AKG C 460 series also has simple, sonically neutral circuitry with frequency response that doesn't vary enough to be audible unless something is seriously wrong. What does vary slightly are the gain, overload point and noise level. For the mikes that they actually manufacture (not the ones made in China), as an estimate let's say that almost any two C 460 amplifiers from the same year are probably within ~1.5 dB for all important parameters. With capsules, however, the tolerance limits are greater; as an equally wild-ass guess, for the better AKG models I'd widen that to ~2.5 dB (the main parameters being frequency response, particularly toward the ends of the audio spectrum, and sensitivity as measured on axis at 1 kHz).
If both capsules of a pair are working well and have similar frequency response, but their sensitivities differ, and so do the gains of the two amplifiers in the pair, then it matters which capsule is used on which amplifier. There's a 50/50 chance that a technician can improve the match between the microphones simply by measuring their gains and sensitivities and with the pieces combined both ways.
If two amplifiers are very different in gain, this can sometimes be due to internal settings (especially for microphones with output transformers and/or build-out resistors); a technician can set them to be alike. Or if that's not the issue, sometimes it pays to replace the FET in an amplifier (along with its bias resistor(s)) even though the existing FET is basically OK, if the gain of one amplifier is near the tolerance limit in either direction and the other amplifier isn't.
The biggest intervention of all would be to rebuild one or both capsules. This should be done only by the factory or by someone with access to identical parts and techniques (a nearly non-existent situation despite some people's claims to the contrary). This entails a large risk, but if one or both capsules were out of spec before, the match could well improve. I've had that experience with a pair of over-40-year-old microphones for which the capsules were rebuilt at the factory; I now have a nearly-matched pair of good sounding mikes, whereas for many years before, they were good sounding, but not well matched as a pair.
--best regards