From ESXi 7.0 Update 3, when you configure NTP on ESXi host, you must not edit /etc/ntp.conf file by hand. You can configure some key parameters by UI and/or command line. If you have to add optional commands like "tos maxdist 30"  in /etc/ntp.conf, you have to create a text file containing NTP configuration commands and load into ESXi NTP configuration by esxcli command.

For more information, see vSphere ESXi 7.0 U3 and later versions configuration files for NTP and PTP can no longer be edited (87176)

To configure specific parameters for NTP on ESXi 7.0 U3 and later versions, you need to load ESXi NTP configuration file by esxcli command instead of editing /etc/ntp.conf directly.

Example:

[root@localhost:~] vi /scratch/ntpconfig.txt
[root@localhost:~] cat /scratch/ntpconfig.txt
server ntpserver.yourdomain.com
tos maxdist 30
[root@localhost:~] esxcli system ntp set -f /scratch/ntpconfig.txt
[root@localhost:~] esxcli system ntp set -e 1