That's how I feel with the cuff. It takes way more work to put it on right to get good readings. Like it's tight around muscle belly but a finger or two can fit under the ends. Or it's just way too tight or loose. I have one spot on my forearm I feel I can get decently consistent but again I also have to spend alot more effort and several runs to ensure I trust it.
I had a friend in the navy that Got doctors to track thier IHB just because an apple watch was giving them warnings and the VA doctor trusted the watch but had them wear a tapped on electric device to thier chest for a week.