Some systems require a unique identifier, but the people who are using a datetime stamp or random number anywhere in their (Luhmann-esque) zettelkasten title (here's a good example) are leading you astray. Doubly so if it occurs at the beginning of the title. There are no affordances in this practice and it's more likely to cause problems at scale. Just say no! (Note this is not the same as using a Luhmann-esque identifier at the start of a title as a means of providing a sort order of one's notes held in an individual folder.)

Are there any reasons for someone to do this?! - perhaps for file name conflicts when digitally inserting notes into a system using third party clients with titles which may cause conflicts (though these could/should be removed later for easier reading); - counterexample: https://hypothes.is/a/Jux0pq7yEe2Uqj9mFXS3nQ - Another potential issue is in shared or collaborative note taking spaces where collision is more likely because others don't have the shared context. - perhaps for forcing sort orders on daily notes or recurring meetings MeetingA YYYY-MM-DD, etc., though these are probably in a separate area of one's box and not in their zettelkasten section.

The point of a zettelkasten is to provide one help in ordering and building their knowledge, not in ordering their notes by time created. This will rarely (sans database-related use cases perhaps) provide any insight and digital systems have other easier and better ways of doing this if you need it.

Worse, some systems may not do autocompletion on words in the middle of titles, so starting a card with a datetime can hamper this functionality. One should check this against their particular system.

Your practice sounds akin to that of the idea of progressive summarization which many do in their overall note taking work.

I generally leave the title for last as well for just this reason. I find these titles are also incredibly helpful in reorganizing slips into broader outline forms for creating new articles.