Switched from Galaxy Watch to Apple, and sleep measurements are terrible.
I was so concerned about the terrible results from the Apple Watch that I did some hard research. Luckily, the problem is not the watch but the software. Not to be an advertiser for this company, but after reading some reviews, I purchased Autosleep. Man, this software is accurate. It used my back data from Health and displayed it properly. The difference is night and day. I am sooooooo happy!