I just ran some tests and I can't reproduce the problem. If I set the level to 75, no devices show up. Set it back down to 45 and 2 devices show up on the list.
One thing to note, if you add devices to HE after setting up the battery monitor, you need to go back into the app and toggle the 'all devices' switch off and then back on or it won't see the new devices.
Ok, hit 'done' to go back to the previous page...wait 30 seconds and click the button to go back to the report. If you still get that screen, go back again and regenerate the report.
I had my hub slow down today. I installed this app a few days ago. I've since paused this app, and rebooted the hub. I'll report back if the slowness returns, or otherwise.
I liked the report and it helped me solve a dodgy device, so I'd like to get it going again.