Sure, all of your switches can get their time sync on your appkiacne but you don't have to configure "ntp master" to it. Just point your switches to it using the command "ntp server [prefer]".
The reason why I don't recommend a Cisco appliance as an authoritative NTP/SNTP server is because the clock chip is similar to a PC. It doesn't have a dedicated method of verifying. You can, however, let your appliance synchronize it's own clock with something that is authoritative. You can get a cheap NTP server that uses GPS (best method so far). Another option is to open a port in the firewall to allow the appliance to talk to world-wide NTP pool using the command "ntp server [prefer]".
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...