Haunting Revenant

I can't seem to find any specifics on this question. When most monsters swallow a creature, the creature becomes restrained. If the Haunting Revenant swallows someone, do they become restrained? Do they have normal attacks? Do they get disadvantage on attacks? All I can see is to cast spells, you have to pass a con save and revenant gets advantage on attacks vs creatures inside it. Does this mean that melee fighters don't have any restrictions inside the revenant?

That's what I was saying. It looks like only magic users are effected inside of it. That just seems odd.