The gourami problem is Iridovirus. They were banned from a lot of countries (like mine) for a long time unless they had a veterinary certification, because the chance of Iridovirus spreading isn't known. It could affect wild stocks.
I doubt the colour varieties are line bred. I suspect a little test tube, gene splicing work a trade secret as
GMO fish are banned in a few lucrative markets, largely for copyright reasons.
The problem with Mycobacter is the farms, and not their stock. In the lifetimes of people I know, tuberculosis was a serious human problem. Antibiotic resistant strains may make it so again. It's a crowding disease, currently often a prisons problem, and fishfarms are pretty crowded places. It's incurable in fish. I caught the fish version years ago (for us it's skin sores, curable by 6 month antibiotic cocktail treatments - don't get it...) so I admit, I've paid a little more attention to it than most.
It's around in the wild and most likely in a great majority of farmed fish, shortening their lives. No one likes to talk about it as it's bad for business, but I have heard up to 85% of fish tested on some farms were carriers. I can cite no sources.
Collect wilds, put them on a fishfarm and bang, watch it spread. I got some fish collected by an acquaintance and left at a fish farm for breeding 6 months after they had arrived, and they all succumbed to tb within a few weeks. New disease, no resistance, easily spread...
You have to wear a mask, gloves and have a shot passport to go to most of the world these days. Intrepid? We have become, if anything; tepid to an extreme.
If you have a for profit medical system, the idea of taking your chances seems fine. There's money to be made from you. If you have a country with socialized medicine, where we all pay for the selfishness of some, then you want to discourage the anti-vaxxer fringe in other countries from coming. They aren't going to respect the rules of the country they visit, so set up rules to make them feel very unwelcome. Every country has ways of deciding who gets in, or not.