In my personal experience if they aren’t fitted correctly they can push the saddle back. I have tried a few types (prestige, fairfax, unicorn tack, protect) and have found it really depends on the horse. Some horses I have really felt a difference on and others I have felt nothing. I personally don’t think I would spend the money on it unless I had trialed the girth and ensured it helped my horse.
I have not had any experience with these girths but if your horse is built in a way that a regular girth pinches and fits incorrectly i think it’s worth it. I don’t think it’s very valuable for a horse that has no issues with the girth