To evaluate how useful/useless adjusted network time is, it could make sense to collect samples?

Be aware that time offsets are expected to be off, as some peers will send the network time as their own time, see commit 14ba286. Also, offsets of 1sec (or a few secs) are expected due to second-precision rounding errors and network delays. Also, larger offsets are expected for some peers that did a -reindex, see commit 0ac42c4.