FWIW, i work as a graphic designer. i was always taught to design logos in all black first -- to nail down the concepts then go and apply color.
just because there is a 1-color version doesn't mean they are abandoning their red-white-and-blue.
The OP is correct that it's similar to the Brooklyn secondary logo.
But for the sixers it's a call-back to earlier logos. the sixers introduced that outline in the late 70s <http://www.sportslogos.net/logos/list_by_team/218/Philadelphia_76ers/>), whereas the Nets are newer to the game with a ball introduced in the 90s <http://www.sportslogos.net/logos/list_by_team/215/New_Jersey_Nets/>
So the new sixers logo in line historically with other 76er logos whereas Brooklyn's logo(s) are all relatively new (and awful if you ask me, which you didn't
)
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haha i started typing my response above, then had to leave to, ironically, present some design sketches to my manager
So bosstown beat me to it...
Calm down. This is just the logo minus the color way. I'm a graphic designer, you always build graphics in b&w to be able to balance the negative space there is no way phillie moves away from the red, white and blue.