some of it sounds almost too good to be true,
Anyway, if Uniquify has spun Hashfast a line of 28nm being good for 4Ghz... then past experience seems to indicate a SHA ASIC will have an absolute maximum of about 1.33Ghz on that, and may need to be dropped to 1Ghz or below to meet power targets. 100 engine chip at 4Ghz, too good to be true. 400 engine chip at 1Ghz, too big to be true.
We believe one previously announced effort at 28nm is using eASIC, so their cores are *much* bigger than they have to be. Of course their startup costs are much lower too, but it impacts the performance a lot. Look at the η-factor for other 28nm designs.