Okay, but you haven't seen an empty right hand, and you haven't seen him actually holding the shield in his right hand. That very first picture was their first teaser on Instagram, and someone may have been holding the shield there because they wanted that angle, but also to have the shield shown.
OR, the shield is magnetic, and maybe it can go on both arms. But I wouldn't leap to the conclusion that we're getting SIX separate arms for this statue, when it would be far simpler for them to switch out the right at the wrist, and just have a mounting system for the shield.
I won't say it's impossible, but eight different pieces would be quite the step up in switchouts from their previous statues. Even the various display options we know they're offering is a big step up.