By training, do you mean for training beginner pilots? I would think there's a lot of benefit from learning on aircraft similar to what you'd pilot post-training.
Yes, changing types will require some training, but it's a big savings if you can get your PPL in a plane with an operating cost of $1/hour. If you look at vendors that are selling production electric aircraft, they claim 70% savings on training operations. That's a big deal. (Link: https://www.pipistrel-aircraft.com/aircraft/electric-flight/...)
Learning to fly at its most basic is much more than just stick-and-rudder skills. There is a lot of information to learn, procedures, airspace, radio work, etc.
It's best to learn how to fly in the simplest safe aircraft possible. Then when you have to learn to operated a very complicated machine you don't even have to think about the flying part.
Complex aircraft are also much more expensive per flight hour, so it makes sense to learn on the cheapest safe thing you can fly then let your employer foot the bill for the type rating.
Also, one specificity of ultralight flying, or at least the way I was taught, is to not trust the engine, no matter how reliable it is supposed to be. One aspect is to make the final approach unpowered. Of course, the engine is still running, but ideally, you should pull the throttle all the way back and leave it here, as if the engine had failed. This is in contrast to the 3° slope commonly taught in general aviation.
Of course, a pilot who only flew on an electric plane needs some time with a flight instructor in order to learn the quirks of gas engines, but that should be quick compared to the time it takes to actually learn how to fly.
Of course nobody's going to be commuting in a sailplane, but they're awesome for pure fun and learning piloting skills.