Q: Is it intentional that only the glaive is a reach polearm?

This was a deliberate design decision: the glaive, guisarme, halberd and ranseur are balanced each other by having different descriptors: e.g. the glaive is reach, the guisarme is trip, the the halberd is set and trip, and the ranseur is disarm. (The damage of each weapon is nearly the same, so there’s no real difference there).