I don't know much about the HA dragon but black has nothing to worry about in the above position after 6...Nf6 7.e5 Nd5.
Why Nc6 first in hyper accelerated dragon?
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Both 4...Nc6 and 4...Bg7 are roughly equally popular in GM play.
The only difference I can see is that Black has different options if White choses a Maróczy setup.
So 4...Bg7 should be perfectly fine.
5.Nxc6 is a bad move, and is followed by another bad move (6.Qd4). Chess isn't played like that.
After 6...Nf6 (6...f6 is also fine) 7.e5 Nd5 8.e6 Black has a pleasant choice between 8...Nf6 and 8...f6. In any case white should try to limit his damage by taking on d7 to reduce Black's central control- after 8...Nf6 9.ef7+? Kxf7 white has only very cheap tricks, and Black a potentially huge center. Technically white is already lost.
8...f6 is very good, too, white is worse after that as well. White's only playable Nxc6 line is after 5.Nc3 Bg6 6.Be3 Nf6 7.Nxc6 bc6 8.e5, which is interesting (and about equal).
Technically, 4...Nc6 is more accurate than 4...Bg7, because Black can enter the Gurgenidze variation when white plays 5.c4!
Black does not have an easy life in the Gurgenidze, but his play is less cramped than in other Maroczy Bind variations.
I came across a problem when playing the hyper accelerated dragon variation of the sicilian. The main line says that Nc6 should be played before fiancettoing the bishop, but I find that dangerous.
Because of that, I usually play Bg7 first. It isn't a problem if the queen takes d4 instead of the knight, but it is now because the knight on b8 isn't on c6 anymore. Why do people play Nc6 first?