Im no expert, there are probably some species in Babycurus genus that are very simlilar. In this case though the difference between B. gigas and B. jacksoni is quite obvious. A quick google search of each separately and then click on images. You will immediately see what i mean.
B. gigas is actually a more attractive scorpion imo, and not quite as common as B. jacksoni. Both are around the same price point.
Yes, the gigas have a darker over all coloration. Especially as juveniles. Specifically the metasoma, the palps, the prosoma, and the first couple segments of the mesosoma. Your dealer will know, probably just a mistake.