Let me be more explicit about that, because my quick response is open to misinterpretation.
With B2 held down as the USB is plugged in, the screen illuminates immediately but without any characters; then within 1 second reads “Reset all?”. This occurs whether the power switch is on or off, and whether the SD card is installed or not. (I have no reason to think that these latter two things would make any difference, I mention them only for completeness.) Releasing B2 before the screen reads “Reset all?” is as if B2 had not been held down; i.e., the screen reads the date and “Connecting….”; Releasing B2 within 2 seconds of plugging in the USB but after the screen reads “Reset all?” does not change the screen, and the Updater does not run.