This natural move is a novelty. It's hard to say without a deeper study whether this is better than the immediate 10...Be6.
1. e2e4  1... e7e5  2. g1f3  2... b8c6  3. f1c4  3... g8f6  4. d2d3  4... d7d5 [%c_effect d5;square;d5;type;Interesting;persistent;true] The belief in the old days was that this very fast advance is bad for Black, but as I've written a few times, the computer shows that everything is more or less playable. 5. e4d5  5... f6d5  6. h2h3 This move is much less played than the main line 6.0-0, and it does seem a little slow. 6... f8e7 Whether this is the best way to develop is something open to question. 7. e1g1  7... d5b6 [%c_effect b6;square;b6;type;GreatFind;persistent;true] 8. c4b3  8... a7a5 [%c_effect a5;square;a5;type;GreatFind;persistent;true] This is an important move for Black, but it's not easy to understand what's the big advantage over the direct 8...Qd6. I think this is clear in the following line: 9. a2a3  9... d8d6  10. f1e1 