The recovery manual (link above in the second message) covers this.

 

Thanks, @Defensor . When I first read that, I thought it was very odd. I would expect most people to use the key blade when the smart key wasn't working. So the scenario I see myself in: my fob doesn't work, so I use the key blade. Then I have to use the fob to start the Defender, but that won't work either. Seems like a flaw of the main use case!