Those are gigs in which the seller (gig provider) will create an "investor ready business plan" and then "supposedly" claim to "promote" that business plan to "investors" and then will "supposedly" claim : "Hey, good news, I have this XYZ bank that is ready to fund you US$XX,XXX or US$XXX,XXX and as part of the process, you first have to open a bank account with them and deposit US$X,XXX".
Now, no doubt that the XYZ bank will be a legit bank. But, the part where XYZ bank has agreed to "fund" the business plan, this part will be a piece to crap.
Now, the buyer of the gig, then becomes horny and goes ahead and opens a bank account in XYZ bank WITH THE REFERENCE / REFERRAL of the gig seller (gig provider) and after opening the account, deposits the US$X,XXX and the REFERENCE / REFERRAL (gig seller) gets his or her referral commission from the bank.
By then the gig in the gig platform is already marked as complete and given a good rating by the gig buyer, because the gig seller is smart enough to have set the gig delivery as something like 4 or 5 days and play the game accordingly upto the point where the gig buyer has opened the bank account at XYZ bank and made that US$X,XXX deposit.
So, overall, it is not perse a scam, but we can say it is a blackhat way of earning some decent referral commissions from banks, with the "leverage" of an online marketplace AND with exploting the greed (and / or stupidity) of people.
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