By "Intermediate UG sizes" I mean if an UG is allowed to be 6 or 9, then 7 or 8 would be an intermediate size.
I'm curious why they are not allowed.
I can't be the only one whose army design iterations often end up with enough spare points to buy one base, but I'm not allowed to buy it.
Mainly for remembering UG break sizes. Just take cavalry 4s or 6s. Last weekend I took an army with both 4's and 6's. Needed to be sure which were the 4's and which were the 6's.
Imagine that I had 4's, 5's and 6's. That is more to keep track of and easier to make mistakes. Warband in 6's, 8's and 9's can pose the biggest tracking problem.
Skirmishers in 6's and 9's is generally manageable. Allowing 7's and 8's as well wouldn't be impossible but would be harder to track. Nothing to stop it in friendly games.
Richard