There's no hard boundary between expletives, grammatical words, and semantic words. And while plenty words sit strictly in one of those categories, some sit right in the border. That's the case of those four words:

• καί / kaí "and"
• ἐνταῦθα / entaûtha "there, here"
• μέν / mén "so, while"
• οὖν / oûn "then"

Even if they're expletives they're really, really far from that sort of babble-like interjection like "shh", "tsk tsk", "umm", "aah" and the likes, so the student is wrong for translating them as such.

However, the ~~instructor~~ destructor is even worse - he's outright butchering their expletive role, and smearing pedantic filth over what's supposed to represent a casual discourse. "Thereupon" my arse dammit, this is the same sort of clown that translates Catullus with the poetic sensibility of a green potato, or that claims Greeks had weird colour vision.

Personally I'd probably go for something like "There was then a review of Cyrus' army and, so, first the foreigners paraded." It sounds rather close to the original - it's casual, but not babble. (Caveat lector: I'm proficient with Latin, but not Greek.)

Note that ancient languages did represent babble too. In Latin for example you see a (ah), fu (blergh), io (yay!) all the time. Specially if you're dealing with Plautus.