I always thought they did...at least in the main game. For example I had infantry and tanks in one bts game, the barbs had riflemen, and most civs had either musketmen or longbows.(though there weren't many left at the time) The barbs didn't have industrialization but they were more advanced then the ai.
How did barbs tech in bts?
I just had an idea for the barbs and tech, it may overcomplicate them a little though:
it would work like you have it now but for each player who does not have x technology barb units using that tech get a cumulative str penalty promo scaled by map size or number of players(y) still in game.(if its possible to use that as a condition)
for example if y=2 -15% str per player, y==3 -10% per player, y==6 -5%, y>=20 -1%
This would kind of simulate the availability of the technology(where they can get their swords and platemail) and also substandard equipment from poor maintenance.(due to lack of understanding of forging techniques for example)