Scroll down in this link , Look at the RV Heater Bypass system diagram and see the position of the valves.
https://www.fretzrv.com/how-to-winterize-your-rv,
Near the water pump:
Opening the 'antifreeze pick up tube valve' to draw antifreeze from the bottle thru the pump and thru the lines is just a 3-way selector valve with the purpose of drawing antifreeze or not. Just to be clear, that's an independent valve and has nothing to do with the bypass system on the WH. The WH should have its own bypass valves if so equipped.
If you see antifreeze on the ground then its coming out a LP drain tube that you left open or its draining out of the water heater drain plug that you left open. But I don't think that's the case because you would see that, it would be obvious.
If that's the case, you are filling the WH and its coming out the WH drain because the bypass valves are in the wrong positions, allowing the WH to not bypass but fill instead. But it appears , as you explained it, that you left a LP drain line open.
If you need to see or understand the system better go to youtube and search 'rv winterizing'.