I have a different experience with horizontal stacked storage of LP’s. While I do not recommend horizontal storage it may not be as risky as some people make it out to be.
I recently cleaned out a room in a relatives house where several hundred albums had been stored for more than thirty years. About half these albums were stacked horizontally and NONE of them are warped.
This room was not heated or cooled and was basically left to the whims of the ambient weather for decades, sometimes it would be 40F and sometimes it could be 90F. No mold, no rot, just dust and some fading due to ambient light.
Your mileage may vary.