And I'll bet that you didn't learn to swim 2 years ago, coming from zero swim background.
This sort of generalization is common for experienced folks. I could make the same comment about cycling or running. A 21 5k for me is so slow that would be a joke for me to race at that speed. Even after a complete layoff for 3 months with zero workouts, it took me 3 workout of under 3 miles each to run under 21 for 5k.
Does that mean it doesn't take any fitness to run a 21 5k? No - it just means I have the background built up in my legs so doing it again is easy. It's so easy for me that I've done a sub-21 5k with a stroller pushing my kid just for fun. That still doesn't mean that because it's easy for me, it should be easy for everyone, and that it's all due to my special running technique. For me to get to this level, I had to train my *** off - sprints, volume, and more sprints. Hurt like hell and no shortcuts.
If your fastest 5k ever was a 30 (and there are many on BT who fall in this category), it'll take a hellacious amount of work to get down to 21.
To say that swimming a sub-24 1.5k is so easy that anyone can do it with zero swim fitness is a load of bull. Sub-24 is near, if not FOP in most Oly races, and likely a better performance than a 21min 5k in a lot of races.
I think you're confusing your natural gifts and/or ability with the reality of the situation. That's the same exact critique I have for Terry Laughlin - it might work for him, but I doubt it works for even a minority. FOP is not commonplace precisely because it takes a combination of technique, talent, and hard work. Or else everyone on BT would be FOP.