I believe it still ahs its arms. The things that it hold behind its back are its arms. It is supposed to be a pokemon that looks down on you and it is holding its arms behind it like some people do to show its superiority.
serperior does has arms, they are about as big as it's middle evolution's, look [link] Serperior is ment to look "sophisticated", thats why they are folded behing it's back, like a gentlemen, and why it's nose is held high.
Actually, if you look close enough Serperior still has arms, they're just folded behind it's back. Look closely at the back sprite and you'll see what I mean. Correct me if I'm wrong, but that's what I saw.
Hay, here's an idea. In some of the older pokedex entries, there some rather disturbing entries that I TOTALLY see A.J. doing, such as example Red/Blue #076 - Golem. "Its boulder-like body is extremely hard. It can easily withstand dynamite blasts without damage." Personally I can see him trying to do that just to see if it was true or not. I also see him trying to chop up poor Staryu and Starmie just to get the jem in the middle, and mistake voltorb for a pokeball.
I've been going through your gallery reading these (which are completely amazingly hilarious, by the way) and I totally just realized that the title is Pokemon Awkward...not Award. My world makes a little more sense now