Generally, that seems to behave properly.

I ran into something else weird while testing. I had Canola2 running, playing music, when I plugged in the charger. It remained lit as expected. Just to check the manual blank, I opened ASUI and pressed blank—but it didn't blank.

I don't remember exactly the next sequence of presses, but I twice got into the state where I pressed Blank, ASUI closed, but the screen did not blank—and, I could not bring up ASUI again (using the power button) until some amount of time (maybe a minute) had passed. Canola2 was running in the foreground this entire time.

Then I closed Canola2, let it sit for a while (still on the charger) and it auto-blanked. I was able to open ASUI at this time and checked the setting: it had been changed to "Never". I toggled it and then ran several tests, changing the setting in ASUI each time, and it behaved properly from that point on, including manually blanking when I pressed the Blank button.

I restarted Canola2 and was able to immediately reproduce the Blank failure. Then I quickly minimized Canola and opened ASUI from the status bar, which worked. But, a long-press on the Blank button was not recognized, nor was a drag across the screen to close ASUI. After a short wait, everything became active again.