People can and should play how they want to. It's a valid method (more valid than A/B/C, if anything) and saying one is "doing the fight the way it was intended" is just wrong. If a full team was supposed to be in the belly, damage from the Unknowns would be significantly higher to necessitate tanks/healers being in there, but damage in there is laughable (unless you're soloing it). If two full teams of DPS were supposed to be outside, then the adds outside would be strong enough that a single tank couldn't hold two of them, but a single tank can easily hold all three. Or, there'd be a DPS check outside as well as inside, but there isn't. Or, the number of people inside would be strictly limited, but it isn't (it might be limited to some number, but that number is much higher than 5, which is a single team's DPS count). Of course, if it was intended that only DPS go in and all DPS go in, there would be no adds in the stomach giving some small purpose to heals/tanks if everyone is horribly undergeared, and there would be no adds outside meaning there's no reason for DPS to stay outside. Neither is intended and both are intended, because SE wants you to play the way that works for you, and they've said in the past that they find it really interesting to see how people decide to handle the mechanics and how they differ from their expectations.
/walloftext