I am a 4.5 level player. When I started tennis back in 1990, I learned with a one handed backhand. I had no issues with my backhand and statistically I had more backhand winners vs forehand. By 2007 (17 years later) I wasn't playing as ofter, I had stopped lifting weights and my shoulder/core muscles were noticeably weaker. Attempting to return hard hit serves with a one handed backhand became a chore. I switched to a two handed backhand. After a year, I felt very comfortable with the two hander. The good thing about the two hander was that it solved the problem of being overpowered with hard serves. The bad thing about the two hander, harder to generate the same amount of topspin as compared to my one hander, less power and I had to take an extra step to get into position as compared to the one hander. Which made setting up for angled shots harder. I hit with the two hander up to 2011. But I started to miss my one hander. I hit the gym again and really worked on my shoulders, lower back and core strength. Switched back to the one hander in 2012 and love'n it again. The topspin and ability to hit angles are far easier with a one hander. But the downside to the one hander is the possibility of being overpowered. If you don't keep your body conditioned, the one hander is not for you. In the end though, I'm glad that I took time to learn the two hander. I know the difference between the strokes based on actual trial and error and not by just what I've read online. In long matches, if my one hander starts getting fatigued, I can switch to the two hander and I'm back in the game. If you have the time and ability, learn both strokes so that YOU know what works best for YOU...also advisable in case you ever decide to teach/coach tennis.
Being there I pretty much concur with everything you said. I think they massively teach 2hbhs in beginners due to a thing with strengh (especially on girls). I think coaches should give the chance to their pupils to try the 1hbh. Especially for those who show a certain pattern and they can always switch back to the 2hbh. They say it's easier for anybody who first learned the 2hbh to switch to the 1hbh because the left hand wouldn't be a liability like in the inverse order.