Add this feature in general to all “semi idle” tasks.
For example having the Trading Post open and searching for items, checking prices, will also get you logged out because you are “idle”.
I believe that the game is detecting idle when really I am clicking away at my task …buying, selling, looking at market prices and yes at the storage where I am sorting moving and examining stuff. My character isn’t moving but my mouse clicking activities are active.
The game’s afk system doesn’t reliably detect anything other than actual character movement. This is commonly seen with people doing long sessions at the trading post or managing inventory, as you found, but can even kick in for things like someone moving people around on an invasion or war roster, or an invasion musket who is motionless but aiming and shooting at mobs.