Cursory glance didn't see this anywhere, but I was playing skirmish offline in Classic mode as GDI and I couldn't build any land vehicles. My screenshot failed and I do not recall the map name, but I remember my build order was helipad first, then war factory. All the land vehicles were greyed out, and if I clicked on what I heard "building" but nothing else happened. I could still buy Orcas.

Also, the original C&C didn't require a barracks for a War Factory, though DTA does ala TS.