This isn't so much a bug I think as much as it is an accidental feature that shouldn't have been added and may have been looked over. I'm aware not all dual wielding features are implemented but this just doesn't make sense

When an enderpearl is in your secondary hand slot, and you have a building block in your primary hand slot, build upwards, and HOLD the right click mouse button... you build, and you also throw an ender pearl.

Since there is a block in my primary hand, it should stop the ability to throw an enderpearl. Although I believe that since you're in the block you want to place before you jump, you cannot place the block and it instead throws an enderpearl.