** Updated below with HPool official statement **
It is very possible that Hpool’s custom client is vulnerable to manipulation and to improve one’s personal payouts at the expense of the network, but it is highly implausible that those fake plots are somehow creating proofs to farm actual blocks with. This is quite literally the problem a blockchain was designed to solve, and I find it extremely unlikely that people have found a way to sign a block based on nothing.
Right now the accusation out of China seems to be that someone can fake the header of a plot with a 16k file and pack a 10TB harddrive with multiple petabytes of “plots”. While its possible that this would fool the client into thinking they are valid plots, and increase the size of your farm in your GUI none of that information is used for network estimates. Network size estimates are based on the quality of the proofs being submitted plus statistical analysis. This is the reason the netspace is always a rolling estimate and will never be perfectly accurate.
What it will not be, however, is 6 EiB off or whatever is being thrown about wherever you read about this issue. If someone is wasting their time with fake plots, let them. This seems like a good reason to avoid untested pooling software regardless of the intentions of the operators, although right now that does look a lot like a ticket back to the “0XCH club”
There is a lot of pent up demand for on-chain pools right now, lets all hope it comes before the dam bursts. Check out Bram’s response below.
Edited 8:25 am EST 06/13/2021
Hpool has provided an official statement on the issue, calling it FUD and saying they are involving lawyers to deal with the accusations.