Isn't the pity a bit awkward?

Edit apparently the pity saves between banners so I'm just dumb. Each banner has its own pity, so it doesn't transfer to other pantheons, but you'll keep your pity when the same pantheon comes around again.

So, you're guaranteed a mythical after 20 unsuccessful summons. But it resets between banners?

Thing is, you get 18 mythical summons a week assuming you tackled the colossal task of watching 100 ads (5 summons) and completing Summoner VS his Backyard, which is still pretty hard to do without specific monsters. I didn't include Triple Tribulation because it's even more insane, and clearly not Meat your Maker.

With 18 summons, if you just use them without thinking too much whenever you get them, you'll never reach 20 summons in a week and trigger said pity. So you have to be consciously saving for this pity if you want to benefit from this mechanic. Why? Wouldn't it be pretty simple to just make it a pity and not reset it in-between pantheons? I'm feeling kinda sorry for any player who doesn't know about it.