a note to the developer mailing list, along with a reference supporting the "correctness" of your proposal is likely to be the fastest way to get the source corrected.
In the meantime, I believe you can edit that file on your device. It looks like it is installed at /usr/lib/lua/luci/sys/zoneinfo/tzdata.lua
It comes via automatic data collection from the zoneinfo data in Ubuntu...
(I usually run the perl script, in LuCI sources /build, to collect the data for the LuCI timezone data update commit.)
Most European cities in CET timezone seem to have the same thing. Not sure, why.
And they have been that way the last 10 years, if you look at the "blame" of that tzdata file in Github
Have you looked at the simple LuCI implementation????
It simply contains the TZ string for each zone.
The update script simply pulls the TZ string from the end of the binary zoneinfo files (in the buildhost). And for some reason, at least Ubuntu seems to have the CET TZ strings this way.
If you want the whole shebang of timezone data, you can install the full zoneinfo package separately into the router, but that is rare.