You're right. The phrase "Cured MS through diet" alone could be a true statement. But to be a true statement it needs to be tested by science. And this doctor isn't doing any real science.

In general when someone says "I cured this chronic, uncurable, disease through diet" I need to read what they say very carefully. At best it's an overblown claim and they actually mean "this food has a strong evidence base to help you manage your illness and reduce relapse". At worst it's evil people cynically cashing in by selling nonsense to desperate dying people.