Please refer to this video: https://youtu.be/SV6PDfDx_5k
TOP shows there are 89 items (there really were I loaded them there), but when I break the drawer I only get items that I got from clicking on the drawer .. so just 2 (1 from first click and second one from second click after the lagged block did not disappear yet)
it doesn't do that with 1x1 drawer, but it does that with 2x2 .. did not try 1x2

Running the FTB Beyond modpack on SpongeForge:
Minecraft: 1.10.2
SpongeAPI: 5.2.0-SNAPSHOT-a3257a0
SpongeForge: 1.10.2-2254-5.2.0-BETA-2254
Minecraft Forge: 12.18.3.2254

Storage Drawer version: StorageDrawers-1.10.2-3.6.1

I think I've seen this mentioned before, and it's specific to Sponge. I don't know why, but either breakBlock isn't getting called, or it's getting called after the tile has been destroyed.

If you know of another open source mod that has an inventory block that lets you "punch" to pull out items, and behaves correctly with Sponge, then I could reference that implementation for the difference.