I just tried this! It actually ended up making the shield face down? lol. Anyway, this is for the 26.1 update that just came out like I think yesterday or the other day. Part of me may wait for optifine and see if maybe it's an optifine thing. I don't know too too much about coding but when I swapped them around the orientation did change, just not to my end goal. Also yes the shield does work correctly in vanilla minecraft. I am super perplexed by what exactly is going on. I think what I may do is copy paste the shield code from the vanilla textures that I grabbed from files and see if inputting it there works. if not then it would clearly be an issue somewhere else besides the sheild.json