It is the PAC 12 now, unfortunately. As a PAC 12 guy, let me take a stab at that. I'm sure it was concerns over speed. The only PAC 12 team that offered him was U of A, running Rich Rods spread option. This is curious as it is still a pass happy league by and large. There has been an arms race for speed starting with Pete Carroll's USC teams and furthered by Chip Kelly at Nikegon. There are a ton of great, fast players that come out of CA every year, so he might not have projected well compared to others with lesser HS resumes. With the exception of Stanford, the WR's in that league are burners. The other issue may have been the league and the level of competition in HS.
That being said, he sounds like a great kid and appears to have great hands. Hopefully teams will be regretting not signing him. Excited to see him in Maroon and Gold.