Here is what happened: at the end of pre-season, the BRR became inaccessible with the message "calculating scores" and stayed like that for hours. BRR then re-opened with season 1 and all player ranks were reset to 1500-2500 SP range. This was normal as players are supposed to start from scratch in each season.
However, there was a glitch in pre-season rewards: they were not based on your pre-season rank. For example champions and icons both got 4 black sports parts. FM fixed the glitch after few hours, and compensated "all" players with 6 black super parts a few days later.
Now, those impatient ones who entered season 1 during the "glitch period" got wrong rewards (4 black sports parts) while whose who waited until the glitch was patched got correct rewards based on their rank (for example icons got 6 black super parts). The compensation reward was given to all players, even those who received correct reward in the first place, so those patient players ended up with 12 black super parts.
You should consider yourself lucky for getting super parts when you should have got super parts as champion 1.