Strange attack movement from AI

[Lord Of Storms]

I am currently playing a campaign (Swiss Mod)and I have been having some strange battles with the HRE in Tyrolia , I love when they attack this province with alot of troops because I can take advantage of the terrain and fend off large armies with a relatively small force. The weird part is when I am defending I place myself High on a slope so the enemy has to climb up to get me (usually quite tired when they get their ) and the HRE would send archers in first and the Royal Knights and other troops would stay behind and walk in silly patterns up and down the mts. ? they do not engage until I wipe out most of the archers, in one instance they did not engage at all but skirted the outer perimeter of the field and just left very strange

[Cazbol]

I've noticed the very same thing in MTW but especially in Shogun. They also walk along your line of archers without engaging, thus exposing their flank and taking heavy casualties. The steeper the hill, the more likely this behaviour becomes.

I'm not sure why they do this but I have a theory. I believe they're trying to drive your archers into or behind your infantry, like they often do with good results on flat maps. If the archers don't retreat as quickly on steep hills as on flatlands because they know the enemy can't reach them as quickly uphill, and if the AI thinks it only has to get as close as on flatland, then the archers may not be driven back at all. If the AI tries this repeatedly we might get such erratic movements from them. This sounds plausible to me, but I'm only guessing.