The funny think about these PCB photos is: The I/O bandwidth bitcoin needs is absolutely pathetic even not worth mentioning. If that were actually a made product they would be very, very stupid to use such a expensive (many pins) packaging for the chips if there were ASICs inside and use it as a bitcoin miner.
There is no doubt in my mind that this is a scam.
However, BGA packages aren't just about I/O. The chip actually dissapates a lot of heat through the pins -- there's a direct all-metal thermal path from the die surface to the PCB through those pins. More pins means more heat dissapation. More pins also means more power entry points on the die surface, so less current per pad, which improves reliability.
So, this is a scam, but even non-scam bitcoin chips would probably come in BGA packages -- but all those pins would be for bringing power in and heat out, not for I/O.
Of course but QFP packages come with a heat pad too and supplying power (ground) can usually archived through these.
Think of it for each of these pins you need to pay for the assembly robot to do one or two repetitions. Internal losses from wires are also not that of an issue if the smallest package dimensions are chosen so the wiring is short.
I mean if those were 20GH 100W chips I could be convinced that those are power pins but even then GPUs come in smaller packages.