Why is ButtonR2 bound with Mouse.Button1Down?

So, when I press ButtonR2 on my gamepad, it fires Button1Down on my mouse.. Why?

It does this both with UserInputService/GetMouse() and ContextActionService

Script:

local uis = game:GetService("UserInputService")
local mouse = game.Players.LocalPlayer:GetMouse()

local cas = game:GetService("ContextActionService")

uis.InputChanged:Connect(function(input)
    local key = input.keyCode
    if (key == Enum.KeyCode.ButtonR2) then
        print("Place")
    end
end)

mouse.Button1Down:Connect(function()
    print("Break")
end)

function placeBlock()
    print("Place")
end

function breakBlock()
    print("Break")
end

cas:BindAction("place", placeBlock, false, Enum.KeyCode.ButtonR2, Enum.UserInputType.MouseButton2)
cas:BindAction("break", breakBlock, false, Enum.KeyCode.ButtonL2, Enum.UserInputType.MouseButton1)