Well first up it certainly is a genuinely dangerous move
You've also hit a basic point about the nature of Williams' book - its
very committed to super aggressive chess even when it goes slightly past the point of soundness.
This isn't anything like the worst case, because it has been the main line for a while, albiet suffering from Rb1 for the moment. But given the stated objectives he could hardly give taking on d4 or some of the slower ideas as his main line!
Mosalenko which I think you've also ordered gives a bunch of ideas here. Also see Nakamura - Shulman from the 2010 US championships. (13.. h6 in the Qxd4 gambit.).
I must admit to a vaguely soft spot for 7 .. Nc6 8 h5 h6 ^ 9 Qg4 o-o or 9 Nf3 Qa5 10 Bd2 o-o but that's because I'm used to 7 Qg4 o-o after which this isn't so scary
None of this is trivial mind. Even 11 Rb1! Qxa3?! (!?) isn't hopeless , cf 12 Rb3 Qa4 13 Qc1 Nd8 14 Ra3 Qc6, or even the bizzare looking 12 Rb3 Qa5!? 13 Rxb7 cd 14 cd Qa4.
The former might be taking weak dark squares a bit far, the latter I dunno.