That's interesting. I tried a Myler bit on a feisty mare I used to ride. I'm not sure which one but it was one of the mildest ones they have and she went in it as if I had a pair of draw reins on her. She felt great at first but gradually she got madder and madder because she didn't like anyone having that much control over her and she had some physical issues that made it difficult for her to bend in certain ways etc. I quit using it after about a week. It felt quite harsh to me and I would want to use one if I didn't have really steady hands. That's just my opinion.
I bought 4 Mylers, a level 2 triple barrel "mullen" full cheek W/ keys, a level 1 loose ring "comfort snaffle", a level 3 D ring snaffle no keys these three bits have the "independent side movement", and a level 3 Kimberwick with keys but without the "independent side movement." Mia, the Arab mare I ride, DID NOT LIKE these bits and she told me vehementally that she did not like these bits by flinging her head around whenever I tried to establish contact. For control I HAD to ride on sagging reins and just tweak the rein for the aids, no contact was allowed on the "independent side movement" bits, and she only allowed sporadic contact with the solid mouthed Kimberwick. Cider, the Arab-Welsh pony I ride has this habit of taking several weeks to make up her mind about something new. We started off GREAT with the full cheek Level 2 triple barrel "mullen" good contact, great response to my hand aids. At the third ride however she started refusing contact and slung her head when I tried to establish contact by urging with my legs. When I tried the Level 3 solid mouthed Kimberwicke (with the curb chain) she also started out good, but by the third ride the good solid contact had morphed into leaning on my hand and she was on her forehand. All of mine are now at the stable in case anyone wants to buy them. I usually keep bits, but if I need to ride a horse on a loose rein without ever taking contact I prefer a curb. I should have known better, I had read their book and come to the conclusion that these bits were made for modern Western Pleasure type movement, but when I found them cheap I decided to try them. They looked SO GOOD, the workmanship simply superb, all the joints moved freely and they felt good to my hand and my arm when I tried them out on me. Later I read on the web that a veterinarian had told a lady that the Myler bits with the "independent side movement" could pinch the horse's tongue. Like any bit out there, some horses with some riders doing a particular type of riding do very well with these bits. For my type of riding, with my hands, the mares both acted totally overfaced with these bits. Both mares were happy to go back to my Dr. Bristol snaffles.
The most telling part of that article is "Five of the horses produced less saliva with the Myler bit than with the snaffle"...NOT a good thing. The more the bit works on the tongue the more problematic (double broken snaffles are for the rare sausage tongues combined with a flat palette). AND how was the horse ridden (in Holland...rollkur/btv/etc)?