I understand what you mean now. No, I don't believe you're misremembering, the titans all came from the Hollow Earth and I think there is room for debate that they can survive it (since Kong seemed completely unaffected by the rapid change in pressure) if they did leave the same way he did but what I think throws this into question is that this assumes that they ALL left through a gravitational inversion portal which (though it was the most direct entrance/exit for humans to Hollow Earth) we see later on in the film that titans are powerful enough to not need one, when Godzilla blew a hole right through the crust and into Hollow Earth directly and Kong wall-climbed back up to the surface. I think it's reasonable that most if not all the titans left without a portal since they were all pretty much hibernating in subterranean territories prior to KG forcing them awake in KOTM.