The reasoning was that one tyre manufacturer had issues and the other didn't. Which also happened to be one Ferrari were on and they were at the height of the Ferrari International Assistance days.
Do they have the fast charge pitstops now? Can't find any info on this, it was supposed to be introduced at the start of last season They've done an indycar and delayed them until midway through the season....though it's been mysteriously quiet on that front. The racing is so good atm I can't imagi...