True - it could be what Camille mentioned. But could also be a case of roots being able to grow where they can. So if the roots can't handle a particular medium (ie. run out of oxygen and die in that medium), then hopefully we can find roots elsewhere - such as above the potting media (if the humidity is able to support it).
If roots don't get supported by both the potting media and the media (eg. humid air) above that potting media, then the orchid isn't going to make it.
Also (maybe) have to keep in mind the things about regular roots and 'adapted' roots. Regular roots handle regular conditions. Adapted roots can handle more moist or more watery or full watery - lower O2 - conditions. So sometimes - if regular roots potted abruptly into media that stays moist or wet for too long, and they take a bad turn - then at least we know what's probably going on.
It is assuming other factors (temperature etc) are under good control.