FYI, Kicksecure 18 is out and 17 will likely be deprecated soon. If you have the time, you might want to give it a shot, it has a lot of neat security improvements over version 17 (like Wayland by default and a “panic button” for instant shutdown).
Using Etc/UTC as a timezone is more of an anonymity measure than a security one, and we generally keep the anonymity enhancements in Whonix. That being said, this does still sound like a useful feature, maybe you could file a request for this at https://codeberg.org/Calamares/calamares/issues?
That would also be a good thing to file a feature request for. Doesn’t look like the feature exists at first glance.