Why isn't the Quad Stash Bundle listed in the Stash Tabs section like the Premium Stash Tab bundle?

It's found in the Bundles, and isn't on sale during the stash tab sale. The bundle price of 4 makes it the same price as individual on sale.

Just seems weird on a consistency basis with the other bundle being in Stash Tabs and also being on sale.

Beacause there isn't a Quad Tab Bundle. The two tab bundles are the Six standard tabs or the Premium Tab Bundle.

Yes there is a bundle. 4 Quad tabs for 500 points. It's under the bundles section. There's also a bundle where you get 1 of each tab and save money. It has Currency, premium, gem, flash, essence, delirium and unique tabs for 435 when it's regularly 526. Why they're hidden from the stash tab section, I'll never know.