Isn't it kind of a useless distinction? I mean it's not like there are so many periods of pre-gunpowder history. We have ancient, medieval and that's it -you could add bronze age but we have so much less records-.

The whole "battles were rare, sieges where common" is a trope I believe some YouTubers started, but I don't think there's any solid pattern. Ancient armies pillaged the countryside to provoke encounters. Steppe peoples did pitched battles all the time because they didn't build walls. Medieval Europe may have had more sieges than battles because of religious homogeneity, but you can see how that model falls down soon in the thirty years war: if you don't engage the enemy they'll loot and pillage you to oblivion. Your people see how you are unable to protect them and desert you.