Ok, I think I get it.
The pre-request script of the folder is simply something that will run before every request in the folder run, and the rules regarding the postman.setNextRequest function still apply - i.e. that it will run AFTER the current request finishes. This means that it looks like the first request MUST complete before the postman.setNextRequest function takes effect (so you cannot skip the first request at all).
I have just come across Iterating only a single request inside a collection with test data specified in a csv file - #6 by nishant.shah2, and in this topic, they used a dummy request as the first request. Iām unsure if this is the best option, but it works.