Yeah, the SNES game is called a sequel but, for a sequel, it recycles a lot of content from the original game. Many of the backgrounds for the fights, while having a bit more details added to them, are clearly lifted from the PC Engine game. In this game, because the merchants were voiced, their sprites are static - they don't blink, they don't talk either.
I'm not sure the fourth girl is a merchant in the first place - she appears when you start a new game in the Advance Mode letting you select a character and difficulty and she also gives you passwords to restore your game. But don't take my word for it because I haven't played the Super Famicom game myself. I've only seen footage of it online.

The SNES version (Battle Tycoon: Flash Hiders SFX) has a 4th merchant with good thumbs again.
Their animations are more on the parsimonious side, though.

Yeah, too bad the artists struggled with the thumbs for the other merchants and now you can't unsee that either.

Woah cute robot girl