With "pick block" rebound to something different say "GRAVE" ( ` above tab) you do not get the same functionality as the default binding.

The "picking" part functions fine however in inventories if an items stack is picked it cannot be duplicated to the slots as you can with the default mouse option. You would often use this functionality in creative when filling an inventory with the same item.

With default key-binding you would hold middle click and move mouse across slots to duplicate those stacks into slots. I would expect that holding the bound key or button and moving the mouse should have the same functionality as this.

This seems to make this creative duplicating functionality unavailable to players with custom keybinds, adapted mice (like a joystick or trackball) or controllers, so possibly a very minor accessibility issue.

To reproduce
Rebind "Pick block" action to something else like ` GRAVE
Try to pick stacks and duplicate stacks to other slots in a creative inventory, functionality is different from default binding.