overall, I would say its not a good idea.
Records are not an even thickness, the label area stands proud and so does the outer edge, it has a thickening or bead designed to guide the stylus into the start groove, it also helps in the manufacturing process.
While stood "almost" vertical is not ideal, I think its better than the combined weight of many pressing down on those at the bottom of the horizontal pile.
Though you could argue, that in the thick sleeve, this can be accommodated.
I think they are stored vertically, purely for ease of use. If you have a horizontal stack, its difficult to pull one from near the bottom and worse trying to return it to the same location.
