Hello again,
When adding members to a class, it seems that filtering a selection does indeed hard-select that single member, and makes adding it simple. However, if your intention is to shift click a group of members, then that filtered selection needs to be hard-clicked (reselected) prior to shift clicking; even if it appears already selected. Is this by design? It seems a little confusing.
As you can see from the gif below, my first click onto the last glyph was actually a shift-click. I had to reselect the left glyph for shift-click to work properly.
