If you case has a sleeper magnet, and you suspend the BB first, it will come on, then go off again. However, I have noticed some third-party cases have the magnet misaligned so it does not work properly.
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I just checked with my case and it didn't visibly come out of standby when I placed it in but when I pulled it out of the holster it came back as if I hadn't put it in standby. Chances are you don't need to worry about accidental keypresses since it seems you do have the magnet in your holster