My theory was nothing special, just that "the boy is being controlled," which seems to be confirmed in the secret ending when you pull the plug and the boy slumps into the same posture as the others when you stop controlling them. My initial theory when I first played the game was that the blob was controlling the boy, but I also realized that wouldn't make sense in the secret ending, and you're right that there isn't really enough information to form any real conclusions.

To be honest, I wouldn't be surprised if the developers meant for the secret ending to confirm the blob is controlling the boy, but didn't think much about it beyond that. Sometimes I wonder if maybe we put more thought into these things than the actual writers do.

"I also get the feeling that this game is more interested in asking questions than providing answers."

Yes, exactly! I also get that feeling. Personally, I think the answer to a lot of the questions is "because it looks cool."

It's so much fun to control the blob, right? Smashing through the glass and walls is so satisfying. And I love the way it moves, how the limbs work together, it's so good. In my opinion, there are not nearly enough games that let you control weird, grotesque creatures, and it's a real shame.