for a given building, excluding Military and Great Buildings
the dojo is not a military building
it is a house
so not doubling the unit is a bug
and to explain that people understand why MILITARY buildings can't give double units
military units are buildings that have unit slot. they don't produce like other buildings: you collect and then the next production starts
but that doesn't apply to military units: you produce a unit: and then?
exactly it occupies that slot and the unit can't be recruited until it died
and that is the reason why MILITARY buildings can't give double units from Blue Galaxie
if it would one slot would need to occupy two units at the same time
and now back to the Dojo
it can give double units. because it doesn't have slots. it produces unattached units
so not giving 2 units is a bug
the difference in short:
military building have unit slots and produce attached units
the dojo is a house that produces unattached units
(and some more points where you will recognize that the Dojo is not a military building:
quests asking to build a military building don't count it. but quests for houses
the output of the Alcatraz isn't affect from it: if it would be a military building Alcatraz would produce those unit because it clearly says it produces the units that are produced in the city)