It is a different variation of her signatures because all humans signatures change.. anyone who's watched any of these dumbass pawnstar type shows would know that. Also if she isn't in DC at the moment to sign the last one, it may have been done with an autopen and the person who set up her autopen may have used older variations of her signature they could find online, because if you look up older signatures online they match the bottom one, not the other three. So it's either a newer variation of her signature, a secretary, or an autopen. All three of which are used by every famous person and all politicians on a near-daily basis.  While it was a good catch, it's a big ol nothing burger that I'm sure will now continue to be brought up as some sort of evidence of something for weeks to come when we have much bigger fish to fry.