I recommend updating the default (and I suppose Safari-specific) User Agent string with each update that includes a WebKit version update.
For example, the latest Orion 99.127 (Beta or RC) reports the following on both my Mojave, Catalina, and Monterey systems (using the Orion downloaded with the OS-specific links):
Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/16.2 Safari/605.1.15
In Orion, I recommend matching the default (and Safari-specfici) User Agent strings to match the latest version of Safari with a similar but not newer WebKit. For example on Monterey with Safari 17.4, this is:
Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.4 Safari/605.1.15
Just to be clear I not suggesting updating the WebKit versions as I understand for whatever reason Apple, etc decided to fix those at some point in the past and report the same 605.1.15 version of WebKit regardless of whatever the reason version of Webkit is behind the scene. I am just suggesting updating the # after the "Version/".
Optionally, also update the listed OS to the actual OS:
Mozilla/5.0 (Macintosh; Intel Mac OS X 12_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.4 Safari/605.1.15
I can't say whether the last one is a good idea and defer to others. As above, the latest Safari on Monterey still reports the OS as Catalina in the OS portion of the User Agent string. Maybe reporting the exact OS version is giving away too much information as far as fingerprinting or OS-specific attacks.
FYI, one site says that Safari 17.3.1 on Sonoma reports this User Agent string:
Mozilla/5.0 (Macintosh; Intel Mac OS X 14_4) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.3.1 Safari/605.1.15
However, I can't verify that one way or another at the moment.
Finally please note I am assuming this is just updating a few strings or resources and/or minor modifications to the code. If for some reason this translates into a whole thing, kill it. Not worth a big investment in time.