Good question. With EA you never know.
Based on how all the other boosts work, the stats will be reduced on every play. The name „RB Receiving“ is only a name not a condition. In the Front Office, the actual description says it reduces stats for HBs and FBs. (Not Limited to pass plays)
I've gone back in old threads about this reducer. Is this reducer only good when your HB or FB is out on receiving plays?
If I do HB Blast or any run plays this will not affect his speed right?