Is it true that iOS devices use a hard coded time.apple.com dns for an ntp server?

I read that the only way to point an IOS device at your own NTP server is to change your dns sever’s record for time.apple.com to point at your NTP server so that when the iOS device requests the time from the hard-coded time.apple.com it returns that NTP server’s is instead of the one apple returns.

Is that true for all versions of iOS and does it work on iPod Touches? Additionally, does it request on port 123 like most NTP clients?

Yes it's true and yes it is very hard coded. Yes it uses standard port 123 UDP.

Jamf is the Apple Business Manager for iOS devices and there is no setting in there either. See https://www.jamf.com/jamf-nation/discussions/11772/ntp-server-for-ipads

Like the article says create an A record for time.apple.com and set the IP to your NTP server and that's it.