A lot of people seem to get caught up in LARPing by following strict rules before they see this usefulness and that rational approach holds back the creativity. It's like getting so caught up in the process of how to have sex that you never figure out how to actually enjoy it.
And yes, the card system would require these rules to make it work because otherwise you might not be able to find anything.
Another issue is that people get carried away with some of the better software for using this system and they end up creating their own rigid system. For example, the power in RoamResearch for me is the most basic features it shipped with. But it could also be a sort of "no-code" platform which people use to "no-code" themselves into a corner. I feel like you should have one "database" in Roam which you use only for this purpose and largely without structure. Make a mess and resist temptation to make it super organized. The more you get caught up in structure, the less you're thinking about exploring your ideas.
The remaining parts of it is the unexpected results for someone who hasn't used this sort of note taking system. The book "How to Take Smart Notes" explains this. You use the notes as a starting point to come up with new ideas. It's useful if you do regular writing, especially as part of work rather than for personal private stuff.
For example, I use this method for jokes. Much of the value is simply having a list in one place. If I want to come up with a new joke, I look at all my material as a branching tree. I can extend a branch by going deeper. I can combine branches to come up with something completely different. I can start green branches. I can write new material all day long by doing this, rather than by waiting for inspiration to nail me.
I think people get too caught up in the technical parts. It's just a branching system of ideas.