If you place a painting facing the "wrong" way and type "/execute as @e[type=painting] run data merge entity @s

" (where N is a non-negative integer), depending on the size, it might move 1 block up or nothing changes. But in reality the painting has faced the other way and it appears that it faces the same way, and if the other way don't support the painting then the painting will break. The only way the painting visually faces the right way is to save and quit then rejoin the world. The same thing happens with item frame and glow item frame except they do visually face the right way but press F3+B to turn on hitbox reveal that they face the wrong way.