Use of 5508 WLC across the WAN as MC for unified access

[Amandeep Mann]

I came accross a remark that Cisco 5508 cannot be used for a MC role/functionality accross the WAN for Cisco 3850/3650 switches in the branch locations (acting as MA). The reason was some 10 ms transit time limits,..But i could not find any such mention in any of the documentation...Does any user have some link to this or perhaps a practical implemention experience.