Yes, that's exactly how Eddie writes. If you are a Brain Knight and you are curretly playing e.g. Reversi 6x6 tournament, you can join another tournament but of some different game type - for example Reversi 8x8 etc. Only Brain Rooks have no tournament restrictions.
I think that everybody who decided to pay for a higher level read carefully all advantages for the level and what is supported for even higher levels only.