With --hostonly dracut includes /etc/systemd/system.conf and journal.conf together with their drop-ins under /etc/systemd/*.conf.d. systemd v255, included in F40 and RHEL10, contains commit 6495361c7d ("meson: add build option for install path of main config files") and it's followup 6378f257e7 ("various: use new config loader instead of config_parse_config_file()") that allows installing the default config files to /usr/lib/systemd instead which is done in RHEL10 (I haven't tested F40).

This is documented in systemd-system.conf (5)

...The main configuration file is either in /usr/lib/systemd/ or /etc/systemd/ and contains commented out entries showing the defaults as a guide to the administrator.
...
In addition to the "main" configuration file, drop-in configuration snippets are read from /usr/lib/systemd/*.conf.d/, /usr/local/lib/systemd/*.conf.d/, and /etc/systemd/*.conf.d/.
...
When packages need to customize the configuration, they can install drop-ins under /usr/ as well.

Thus dracut also needs to include the new config files and drop-ins from /usr.