Perhaps the whole point is that it'd be open to interpretation
I think that is exactly what the point is. There are some pretty awesome videos out there where people have seriously gone in-depth in their interpretation of the game and the ending. some of them are hours long and discuss literally every "level" of the game. It's almost like a master's thesis the amount of time some people have put into dissecting this gem of a game.
This guy's accent is a little difficult to understand but at the 13 minute mark he goes into some very interesting details about the ending once you turn into the blob.
Obviously there are complete spoilers in this so for anyone that hasn't played the game, don't watch that. Inside is one of my favorite games ever and it is specifically because of the vague story that this is the case for me.