Uh, I don't even keep hillstream loaches and even I know that fast-moving water is almost a requirement for these guys.
Restricted to shallow, fast-flowing, highly-oxygenated headwaters and tributaries characterised by stretches of riffles and runs broken up by pools or cascades in some cases.
Substrates are normally composed of bedrock, sand and gravel with jumbles of boulders, and while riparian vegetation is often well-developed aquatic plants are typically absent.
The most favourable habitats contain clear, oxygen-saturated water which, allied with the sun, facilitates the development of a rich biofilm carpeting submerged surfaces.
SeriouslyFish.com which I feel is one of the best resources related to fish says the above.
Also, I would think that their body shape is like it is because they have adapted to live in these fast flowing waters.
Most importantly the water must be clean and well-oxygenated so we suggest the use of an over-sized filter as a minimum requirement. Turnover should ideally be in excess of 15-20 times per hour so additional powerheads, airstones, etc., should be employed as necessary.
Many fish can adapt to conditions outside of their desired environment. As you would know with bettas, there is a huge difference between surviving and thriving. I'm sure if you put your loach into a species specific tank you would notice the difference.
Also, just because someone is posting on a forum doesn't mean that they don't know what they are talking about. I don't have any qualifications but I'm sure I know more about wild bettas than 90% of this forum.