Army sizes relative to technology was a little bit of a simplification on my part. It’s not just the agricultural technology, that has more to do with general population size which affects army sizes of course, but it’s more so the societal structure, feudal armies are just not that big. They’re too decentralized to support armies like that for that long. For an example from our own history, it’s why Roman armies were so much larger than medieval armies, despite the Middle Ages having the same or better agricultural technology and similar population sizes in Europe.
Now I should say, this stuff doesn’t bother me all that much, it doesn’t really ruin my experience reading. But I am a historian so it just stands out to me more when reading lol.