The change is definitely fairer for those on S9, so thank you, but very much more unfair for S1-8,10,11 lower level, casual players. 26k stamina is a LOT - over 400 boost items - so this will unfortunately encourage hoarding even more. I've been saving 2 weeks and have amassed 120 boost items and 5000 regular stamina, which is barely half the 26k! In theory I could save for 2 further weeks before spending it all, but as I said this is hoarding.
I suspect that they chose this item over a flat XP item not because of careful consideration, but because it was already programmed in lol.
All in all, it's a nice reward and surely appreciated (as an S9 player I am grateful), but will now benefit big spenders much more than the rest of us.