whatever. still i don't think this is a nadal-only feat. pretty sure federer, as well as other former number 1s, had a positive h2h against their top 10 oppositions before at some point during their number 1 stay. for me the true meaning of domination against top 10 players is the winning streak against them.
After looking into it a little, it seems that Federer may actually never have achieved this feat. In fact, it seems he lost out on attaining this distinction by the very narrowest of margins on multiple occasions.
I looked at the 3 players most relevant to Fed's h2h against the top 10: Hewitt, Nalbandian, and Nadal.
Federer gained winning h2h against Hewitt at the TMC 2004, which happened around Nov 15. Before that, Hewitt had an equal or better h2h.
Federer gained winning h2h against Nalbandian in Madrid 2006.
Federer has never had a winning h2h against Nadal.
Federer entered top 10 on May 20, 2002 (he dropped out and re-entered permanently later that year, but that isn't relevant to this).
Hewitt was already in top 10 with a winning h2h against Roger.
Hewitt drops out of top 10 intermittently from Nov 2003 to May 2004.
During this time, Nalbandian is always in the top 10 (always ranked 8th or 9th, to be precise, and he had only re-entered the top 10 on Sep 3 of that year, exactly
two months prior to when Hewitt dropped out).
Hewitt would not leave the top 10 again until 2006, but Fed gains winning h2h against him in Nov 2004.
At the time, Nalbandian is in the top 10 and has a winning h2h against Fed.
Nadal entered the top 10 on April 25, 2005. Since that time, Roger has never held a winning h2h against all of the top 10.
Two weeks later, on May 9 2005, Nalbandian drops out of the top 10 after having been at the 9th or 10th spot from Nov 2004 to May 2005.
So that covers all of Federer's stay in the top 10 up to this point. Indeed, he missed the boat by the very narrowest of margins.