> Intelligence is just as much about knowing what to throw away as what to keep.
Sure, but you can see it as two steps. Decide what doesn't matter at all, and throw it away. Then compress the rest losslessly (according to how surprising it is, basically the only way)
I think a theory of mind based on data compression is backwards, for this reason. When you have "data", you've already decided what's important. Every time you combine "A" and "B" into a set, you have already decided
1. That they are similar in some way you care about
2. That they're distinct in some way you care about (otherwise, it would be the same element!)
... and you do this every time you even add two numbers, or do anything remotely more interesting with "data". There is no "data" without making a-scientific statements about what's important, what's interesting, what's meaningful, what matters etc.