I know right? I don’t like it when people “on our side” talk out of their arse about this. I conclude that people (on either side) who tout this are either incredibly ignorant or lying.
The 25th amendment provides a way to fill a vacancy in the Vice Presidency and has been used in that way twice. But if both President and Vice President were to die at the same time and the Speaker of the House became Acting President, there doesn't seem to be a way to select a new VP. Of course if Nancy Pelosi became Acting President she would try to get people to consider her the President.