You are definitely onto something. Lets upvote this to the top.
As posted by Freewar on the forum of the Nexus mod in question:
'THE RESULTS ARE IN. THIS IS THE ACTUAL SIEGE FIX WE HAVE BEEN WAITING FOR.
Siege towers actually work now. Like 80% of the time you will see all three lanes at max capacity with only minor gaps between usage.
I had one situation where some bots at the foot of the siege tower all decided at the same time they needed to go somewhere else and that blocked everybody else who wanted to climb, but that lasted only for a minute or so, but issues such as defenders climbing down, attackers climbing back down and general under usage are really gone with this mod outside of the situation I have just described. This fix is absolutely insane, we waited 565 days for this. Thank you very much ZiggyBoy!'