"couldn't have done" VS "couldn't do" in this example

Question

A: The original plan was to start from the tree line at the bottom of the mountain but the explorers couldn’t set up camp there because of the rain so they moved higher up.

B: The Robertson team should have known that they couldn’t have started from the tree line in the rainy season.

A: Yes, they really should have checked that!

What is the difference if I rewrite it as

The Robertson team should have known that they couldn’t start from the tree line in the rainy season.

The prior phrase "should have known" further reduces my ability to think. I don't know if its existence makes a difference.

Answer 1

While it can be justified, it's not necessary. "Couldn't start" would work too and be clearer.

There are two readings for the perfect here. One is a conclusion based on evidence.

I left at four and he left at five. He couldn't have gotten there before me. [I conclude that this was impossible and did not happen.]

This reading is much more prominent the second one.

The second meaning is that they realized they would not be able to be in a position where they had started from the tree line. In other words, to have started from the tree line was impossible.

While this reading makes perfect sense, it adds unnecessary complexity. It goes to the past (E0) and pictures an internal future (E2) from which to look back at an internal other past (E1).

By contrast, "they couldn't start" means that they realized they would not be able to start, that it was impossible for them to start. Hence, we only have a past event (E0) looking ahead to an internal future (E1) or to a simultaneous impossibility, which is much simpler to grasp.

Because of that, I would either go for the "conclusion" reading or suggest that the writer replace it with "couldn't start".