/* Let's try to make sure that the clock is always
* monotonically increasing, by saving the clock whenever we
* have a new NTP time, or when we shut down, and restoring it
* when we start again. This is particularly helpful on
* systems lacking a battery backed RTC. We also will adjust
* the time to at least the build time of systemd. */
So i think the "epoch" of when systemd is built + the stored /var/lib/systemd/timesync/clock achieves the equivalent functionality of increasing time between boots. And ensuring the very first boot is "recentish".
/* Let's try to make sure that the clock is always
* monotonically increasing, by saving the clock whenever we
* have a new NTP time, or when we shut down, and restoring it
* when we start again. This is particularly helpful on
* systems lacking a battery backed RTC. We also will adjust
* the time to at least the build time of systemd. */
So i think the "epoch" of when systemd is built + the stored /var/lib/ systemd/ timesync/ clock achieves the equivalent functionality of increasing time between boots. And ensuring the very first boot is "recentish".