Title is fairly self-explanatory. Right now, when in a filtered view, if you click the Select All checkbox of a list of sub-items, all sub-items including hidden ones, are selected. This is not an expected UI behaviour and could easily break things.
For example, say I am reviewing all of my own tasks using a filter view for sub-items assigned to me and marked as anything other than Done. In one item I have 15 sub-items that are all completed and need to be marked done. I can’t simply click the Select All and change the status of just MY sub-items to Done. It selects all sub-items in the item.