I have no clue. Maybe he's too overenthusiastic for his own good. Maybe he has poor judgment and thinks it's no biggie or believes he can't get caught. Maybe he looks up to CBOAT and wants to be the next big leaker.
All of those seem more likely than "Hey NeoGAF, my name is Spil Phencer, here is 90% of Microsoft's first party strategy for 2014 minus whatever timed exclusive DLC we I mean they announce at E3 and also tentative target dates for 2016 games that haven't been announced yet, please ignore the next batch of sales numbers."
I don't think this would be done so people don't look at sales numbers. I think it's done because ms have just received their sales numbers and an estimation of sonys and they're hoping to reinvigorate the platform. Honestly, not much was really leaked if you slow down and look back:
Forza horizon 2 - well yea, already suspected strongly.
GoW 2016 - work started jan 20th, 2016 makes perfect sense.
Halo 2 - this is the main one, but is not out of this world as we already had halo anniversary and this is masking halo 5 delay.
Halo tv show - already leaked
Crackdown - Phil Spencer's worst kept secret
Titanfall bundle - not that surprising, we've seen the controller and marketing is big, if it was a controlled leak this would need to be announced soon anyway so why not do it like this and create some buzz about it?
White xb1 - been rumored before
Platinum game - already rumored
MS haven't really let the cat out of the bag on much here at all, most were rumored and nothing is confirmed by this, yet people are talking about xb1 right now and not tomb raider performance or machinima or drm.
I don't think this is to hide npd, I think it's because of the contents of npd.