I don't think that's necessary.
So, they are either a lawyer who has done it for hundreds of clients worth $300M+, or they are lying.
I see they claimed to "do it for a living". I see where they say it only makes sense for clients with 300M+ net worth.
There are plenty of other ways to interpret those two points. For instance, it may be a thing they do at their job, but not the only thing they do.
I don't think that's necessary.