Another way to look at it is that it doesnt (afaik) have externsl context, so there are severe limits on what it could possibly infer from some code. Like you say, if something unusual is being done because of a library, or business rules or something, "AI" cannot take this into account. There may be some cases where something non-obvious can be distilled out of the code, though I agree that mostly the stuff you can infer without context is mostly self evident from the code anyway

Edit: just thinking, the canonical example would be something like the fast inverse square root from quake. Is it going to summarize or is it going to tell you

  i = 0x5f3759df - (i >> 1);

  // Shift i right by one and subtract it from 0x5f...

(It would be cool if it does work here, even if it does, when someone makes up a new thing like this, it couldn't possibly comprehend why it's being done)