> perhaps he uses a double throw switch, which both disconnects
> the 7805 from the PIC's Vdd lines and also shorts the PIC's Vdd
> lines

That's the best way to ensure a power-down reset. Circuits can
behave oddly (don't I know it !!) if Vdd doesn't go low enough
when the power switch is turned off before power is re-applied.
It's recommended in the electrical specs that Vdd reaches Vss
before power-up, and shorting the Vdd and Vss pins with a switch
as or after the power supply is disconnected pretty much guarantees
that

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