If you actually read the description you will realise the Season XP booster only boosts so you get gains from stuff that gives normal XP.
You get 50 Season XP /10000 regular XP instead of 25 Season XP/10000 regular.
It is a rubbish award.
I added up all the xp available from my quest list, comes to about 300k xp.
300k xp = 750 Season xp . Use the booster before handing them all in and I get 1500Season xp.
Doing 4 Bingo cards gives me about the same amount.
300k XP worth of quests would take me many days
4 Bingo cards can be done in minutes.
Blame the people who announced how to do the whole season in 2 hours which made the Devs change things.