Kibe version: 1.4.3
Minecraft version: 1.16.2
Modpack: All of Fabric 3 v2.0.5 (with removed mods from v2.0.4 readded)

I had 3 tanks placed on top of each other, with liquid XP entirely filling the lowest tank block, and a little bit more in the middle one. I placed the XP Shower on the side of the top tank block. Doing so did not have it pull out any XP - it can only pull out of the tank block it's currently attached to.

(Unrelated: thanks for this mod!! It's great seeing all of these cool features from OpenBlocks and elsewhere implemented in a modern Fabric mod. The rework of the old Ender Storage mod is especially cool. Hope to see more from you!)

Hi, glad you liked the mod!
This is actually intended behaviour, Kibe's tanks are gravity based, so you can only extract fluid when the tank actually has fluid... If you want a non-gravity based tank you can use Industrial Revolution ones, but they only stack vertically.