A crossbow comes from the same era too. Classical is Horse Archers(6) Swordsman(6) and Crossbows(6)... I am pretty sure machinery is classical.
There is no classical spear I don't think, but spears can hold out pretty easy.
I don't think any str bonuses should be given in eras as a UU benefit IMO. So, Keshiks would also have to be modified IMO I think. I haven't gotten to Mongolia yet. All in time.
Machinery seems expensive for the classical techs though. Some ways more expensive than early medeival techs.
Machinery is a Medieval Era tech--I checked in the XML to make sure. So, unless they have changed that in the patch, it's still a Medieval Tech. The other classical era units, I believe, are Elephants and Catapults (can someone else verify that?).