It is the straightforward assumption that house ape was used to refer to the original posters son returned from adulthood and with a negative connotation. That is why the assumption was made. I cannot imagine what other use you could have imagined given such clear context.
That I would use it in a context/audience that wasn't my children. I personally find that an odd default assumption.
I under no circumstance assumed that OP says "house ape" to his sons face .... did you?
Maybe I'm the odd duck here.
It's clearly about his son, though I don't assume he says it straight to his face. I thought you were also thinking of your offspring. Sorry I've misunderstood.