If you set the "Use Item/Place Block" setting in Options > Controls, interacting with bundles will use right mouse button no matter what.

This is really unintuitive because the control is named "Use Item", and therefore may cause confusion for players with custom control settings.

Reproduction:

1. Go to Options > Controls > Use Item/Place Block, and set it to a custom keybind

2. Go in a world and take a bundle

3. Attempting to use the custom keybind on the bundle fails, but right click still works