Where did you see that info ? As far as I know buses are not included.
The only exceptions are rail replacement buses, even on some disused lines. However staff doesn't always know that it is valid.
I've never heard of this. Please provide a link to where you found the information.
The buses organised by SNCF are included. Some regions have more, some not so many. In Alsace for example you'll find a 2-hourly TER bus St. Dié to Sélestat. Passes are valid. If the driver looks puzzled, then I usually say it's an SNCF ticket (“C’est un billet SNCF”). That usually helps, or else show their bus, below the QR code on the mobile pass. That recently helped in the bus from Verdun to Meuse TGV.