It's just that I have seen projects delay making an important decision by rationalizing that there is not enough information and that the decision can be made later.

Then it turns out that the vital piece which fits the requirements does not exist at all (or does not exist for small time customer), or is incompatible with the architecture which has a lot of resources invested in.

Not saying that this will be what happens and most likely Librem team are already well aware of this risk, but it is certainly a possibility.