Fowles was part of the original pool in 2007. She was selected to the National team pool in the spring of '07, her Junior year at LSU, more than a year before the 2008 Olympics.
. She came into the pool with Parker, C. Paris, and Jess Davenport. This time around, Griner and 'Sloot were added in spring of 2011, again more than 1 year before the Olympics. Sophia Young was the lone late addition to the pool this past January, IIRC. Shortly after that, in February, the Committee was already starting to make the first round of cuts.
So again, the real question should be: Why didn't Nneka make the pool in spring 2011 after her Junior season? She was clearly a great collegian at that time but apparently not impressive enough to be added at the same time as Griner and 'Sloot. That was probably the real opportunity missed; everybody else except Sophia Young was already in the pool. So fast forward to Nneka's senior season. By the time Young was added--which looks like about the final timeframe that the Committee considered adding players before cuts began--how many more big/notable games did Stanford have that might have caught the Committee's attention? They had a good win at Texas, but Nneka was dinged up and I don't believe she played. She played well and was the Cardinal's leading scorer with 22 at UCONN, but KML had 25 and Stanford lost the game. Then around the holidays she goes absolutely NUTS at home against Tennessee. 40+ points and a gazillion rebounds. Definitely a statement game for the ages that served notice she was taking it to another level. But by that point in her senior season (January) that was the only game against a big-name program that really stood out (and boy did it stand out...) that they hadn't already seen in spring 2011. So, the committee decided to take a pass when they could have added her along with Sophia Young. And in January 2012 the pool already had 12 players who could be labelled forwards or combo forwards. Nneka would have made it 13. At its largest, the 2007-08 pool had 11. Maybe the Committee was close to talking her but thought by adding Young they had added another new, athletic forward to the mix and that was enough. I would have to think they took a hard look at Nneka, not just for talent but also for the youth movement that you rightly identify as a necessary ingredient in the larger process.
For whatever reason, they didn't, and it may have been largely due to the fact that after she wasn't picked for the pool in spring 2011, there were not--IIRC--any opportunities for her to scrimmage or play against them or against other pro talent like she did as part of a Select team in 2010 before the WC. That team, and the national pool team, played and scrimmaged against each other, and later the national pool team had its own scrimmages internally as cuts progressed. I think that final cuts for the 2010 WC team didn't occur until almost right before the Championships began in September. In contrast, Sophia Young had already been an WNBA all-star and was looking good in her 2011 WNBA season. She may also have had a partial overseas season under her belt by the end of 2011. If there were any games in 2011 between the national pool team and a Select team that included collegians, I don't remember any. (Not saying there weren't.) Anyway, final cuts for this Olympic team were made way in advance, unlike the WC team.
To repeat what I said in another post,
I think Nneka is clearly one of a handful of people who could be put on this team right now, if the process were set up that way, and play great ball for Team USA. IMO she is at that level, and she has the youth element on her side. (Lawson is another who could easily play great ball for us right now. She's having a great year and could suit up tomorrow.) But too many people are mixing what they've seen in this WNBA season--or in Nneka's case, all games after December 2011--and basing their opinions on that
in addition to what they saw earlier in her college career. The Committee had a schedule that appears to show January 2012 was the last opportunity to get added. Cuts began thereafter. Certainly there were people in 2011 and early 2012, particularly after the Tennessee game, who saw Nneka and said "She should be on that team." Not an unreasonable position AT ALL. But for reasons above, mostly having to do with timing, it didn't happen. One last unfortunate reason for her 2011 omission may well have been the
huge amount of press Griner was getting and continues to get, which sucked most of the air out of the room when it came to collegians on the team, even though 'Sloot broke through the noise.
I love Nneka and our USA team. If I had the time and money, I'd be London cheering them on. Yeah, BG won every award, but not everyone agreed with it. Just like I'm sure you don't agree with me that Nneka is better than Young. 
