[Client] IP/XP rewards timer decreases even when no rewards are given.

I'm not 100% sure if this is intended or not, but I feel like it shouldn't be intended.

Say I create a custom game with only me in it (and some bots). It tells me no rewards will be given because there are not enough human players (both before and after the game). I understand that part. What I don't quite understand is why does it still deduct the match time from my daily allotted custom rewards if I don't get any rewards from playing that match?

EG: If I have 88 minutes of rewards left and play a game by myself for 14 minutes, it says afterwards I have 74 minutes of rewards left even though I never received any rewards from that game.

Thanks for any reply.

EDIT: This is not about using XP/IP boosts, this is about the 120 minutes of daily custom game rewards allowed (for level 30 summoners, I think it's different for lower level summoners).