Norse Infantry - Arbitrary building speeds

Currently, several of the Norse Infantry units build their buildings correctly on time, whereas other Norse Infantry units take twice as long to build their buildings.

Melee Scout, Spearman, Harjar, and Ulfheoinn take twice as long to build buildings compared to Throwing Axemen, Berserkers, Chief, and Ranged Scout.

As there is no other in-game indication that Scouts, Spearman, Harjar, and Ulfheoinn should take twice as long to make a building, I am putting this forward as a bug.