Yeah it does seem strange. I use their Premium and it’s costing me £1.49 a year so who knows.
It seems to be pretty accurate for me. Last night it tracked that I didn’t get to sleep until about 40 minutes after starting it and going to bed, which feels about right.
It asks me to place it on my bedside table rather than balancing it on my bed, and it does use the microphone.
Maybe the Android app isn’t as good, if you’re using the latest version of Android.
I think I remember seeing when I first started using it, or switched between the microphone and accelerometer options (on iOS) that it takes a couple of nights for it to settle down/become more accurate? No idea if this is actually true, but could be worth trying it out for longer if you’re so inclined
Based on the Play Store description it looks like the Android app only uses the accelerometer instead of the microphone option available on iOS