If you have a building with multiple upgrades which you want to limit the number of all forms (eg a command centre with orbital command and planetary fortress) then you need to give all forms of the unit the same alias string and use that alias string as the requirement unit type.
If you have a building with multiple upgrades which you want to limit the number of all forms (eg a command centre with orbital command and planetary fortress) then you need to give all forms of the unit the same alias string and use that alias string as the requirement unit type.