From an IMABI tutorial on the と particle:
It appears the lesson is that the noun marked by と/に marks the "basis of comparison", or the thing which other things are being compared to.
Question: Shouldn't (31d) ("その父は息子と似ている") also be marked as incorrect here, since 息子 is being marked by と and the subject of comparison is intended to be 父?
I think both the points made in user3856370's answer and
they both make the second person the basis of comparison when ..
are true. But they are not clear distinctions.
Adapted from here,
1 are both fine and 2 are both wrong. This should be what the textbook says - 'the basis of comparison' does not differ regardless of に/と.
That said, as user3856370's answer says, there is natural difference coming from 'に/to' and 'と/with': The former suggests 'look-alike-ness' goes in one direction and the latter in both directions. This makes 31e more odd than 31d, due to the common sense about inheritance.
To me, 31d is acceptable but may be marked rather as ?.
The lesson is saying that with と both sides of the comparison have equal weight. There is no standard that the other is referenced against. They both share the same characteristics.
With に the lesson says that this is marking the standard of comparison. It is the thing that something else is compared to. In this case the father should be the standard of comparison and be marked with に. It makes sense to say that the son resembles the father, but it's a bit weird to say that the father resembles the son.
I guess in English you could translate その父は息子と似てる as "the the father and son look alike", whereas その父は息子に似てる would be "the father resembles the son".
In summary, 31d is fine because no standard of comparison is being made.
Edit:
Actually, I see what you mean now. The part that says "they both make the second person the basis of comparison when ...". That's confusing. I think 31d is fine, but better wait for someone more knowledgeable to give a definitive answer.
