systemd uses timeX.google.com as default time servers and this appears to have not been changed by Solus. Upstream was asked by Google to stop using timeX.google.com as their default time servers. However, the servers were left as a default, and only a configure-time warning was added. These servers use a non-standard concept of time and are only intended for use in Google's data centers, not by the public.
It would probably be a good idea to default to a NTP vendor pool instead.
Reopening. systemd's "solution" seems to be --with-ntp-server to change ntp pools for systemd.
Took the initiative, sent out an application for Solus for an NTP vendor pool allocation. Currently awaiting a response.
If we stop using google for ntp server, I guess it would make sense to also stop using it as primary source for dns servers, which can be done with -Ddns-servers. DNS from Quad9 and Cloudflare could for example be used.
Okay so, I've tried on multiple occasions to reach out with an application for an NTP vendor pool allocation and haven't ever heard anything back. Marking this as WONTFIX.