It should help your streamline and remove any splaying of the legs, so its not totally a crutch. But also make sure you are getting a solid catch rather than a soft catch and slip (because the propulsion from the legs can now overcome your bad catch).

It should help, but it can turn into a crutch. Also the oxygen load from your legs goes up, so you will have less oxygen to give the upper body and apply force with if using for full stroke. If using for kicking on side, kicking on back, dolphin kicking on front and back then no issues, it will help for sure.