The FiA has tweaked the rules in readiness for the fracas that will be because of the engine related grid penalties for the upcoming season.
"A change to the power unit penalty system was also approved, whereby if a driver incurs a penalty exceeding 15 grid places he will be required to start the race from the back of the starting grid. If more than one driver receives such a penalty they will be arranged at the back of the grid in the order in which the offences were committed."
Apparently, it's to make things less confusing for the fans.
https://www.fia.com/news/fia-announc...il-decisions-8