Lloyd and others.
I've run KES 6.3 on K 6.2 and 6.3 (my own on-premises server). I've not experienced ANY problems with profiles not working, firewalls blocking or anything else like that. I had an issue I initially mistook for a firewall problem, but it was simply the client turning off his machine during a KES install. False alarm.
As far as I can see in this thread, there is only ONE person with an issue - jamesm sherman. Looks like an isolated case.
I see no reason to to recommend KES 6.3 / K 6.3 to everyone.