I think you're correct, but sysprep is what resets the CMID. See this article: KMS Host Client Count not Increasing Due to Duplicate CMID'S - Ask the Core Team - Site Home - TechNet Blogs
BTW - I haven't tried resetting the CMID using the /rearm command, but that might be worth a try to get the count up without having to go through the sysprep process 25 times. 
Geoff