Hmmmm, . I am definitely NOT a neurologist, so I won't refute what he/she said to you. I generally find doctors to be pretty cautious about making statements like this, so I am a little surprised you were told this. But then, I don't want to say that super annoying doctor thing of "Hope for the best, but prepare for the worst".
A neurologist is an expert and they may be able to make a pretty good prediction, based on your disease course and their knowledge of the disease. And frankly, there are plenty of folks who don't develop aggressive forms of MS. We're still learning a LOT about MS. And, a locum neurologist is a specialized specialist, so there's that. They (hopefully) really know their stuff.
MS is definitely a snowflake disease, which means every person responds to it a little uniquely. And, I get not trusting someone's sweeping statement. I would be interested to hear what the other two neurologists told you.
In the end, if two out of three or all three offered relatively good prognoses, that's not a bad thing.
Best, Erin, MultipleSclerosis.net Team Member.