For some reason they recommend against directly forwarding Jellyfin's ports, but reverse proxies are fine. I expect this is because the default configuration doesn't use SSL.
This smug mentality that security is unnecessary when exposing ports to the open internet reminds me of people who think its fine to drive drunk because "I've done it dozens of times before and nothing happened!" It also reminds me of the mentality of tech company VPs right before they have a massive data breach. It's quite absurd to read.
I think you'll find without exposing ports to the open internet we would not be having this conversation right now. Which, I suppose, wouldn't be such a bad thing.
I'm not a radar operator but I'm pretty sure that's not how it works. Banging on the hull doesn't produce radar emissions.