Under the hood your list of userLists is just a list of unique ids (list of texts)
So on page load you are only loading that lists of texts. The Things themselves are not cached. It is as soon as you need information from a field of those userLists that Bubble will need to go a layer deeper and turn that unique id into a Bubble Thing/object.
I do not know if Bubble needs to convert all of the unique ids in your list into Things at that point, or if it can just convert the one you need. Not sure on which one it would do.
You are seeing searches in your logs just from referencing a list though? That doesn’t sound right.
There was an interesting find by @joeyg regarding multiple references to Current User: Work Unit Test on Current User