add selected items to existing device collection button

Can anyone explain if there's a difference between the "add selected items to existing device collection" button and "add selected items to existing device collection" right-click  option? A colleague attempted to add about 35 devices from a base collection to a new collection using the button. However, when he refreshed the new collection, all 150 devices was copied from the base collection to the new one. Another thing we noticed was the option to remove device from collect is also grayed out in the new collection.

But if you right-click on the objects in the base collection and choose "add selected items to existing device collection", only the selected objects are added to the new collection and not all 150 devices. Also, the option to remove selected device from collection is available and not grayed out like above.

Can anyone suggest an explanation on why there is a differences regarding to the quirk that we observed at work?

Thank you,
- Tuan