I don't think Finland has high confidence that the binding agreement will save them.
If you look at the polling for if Finland should join Nato there is a huge spike after 2022 [1]. Even Sweden which has a buffer between it and Russia also had a increase in polls [2]. Not that anybody does this poll, but you won't see a spike in if say Canada should join the EU. The point being, these countries do not trust that the EU will protect them.