I have one sister that was diagnosed in her 30’s and a co-worker that was also diagnosed in her 30’s with MS. Neither one has it now. It has mysteriously disappeared.
Diagnosis is sketchy especially early in the progression. Plus, there is a remitting form of MS in which a person may become asymptomatic for periods of time. Hopefully your friends had a wrong dx, or at least the relapsing/remitting form, which is more treatable than the straight progressive illness.