Dave Meltzer wrote an explanation for the NXT picks in the new Wrestling Observer.
A key here is political. With the exception of Balor, who was in NXT for far too long, everyone called up was someone signed and trained by WWE and put in their system. People like Aries, Roode, Tye Dillinger and Eric Young, not to mention the champions of the brand are all far more advanced, but because of the millions of dollars spent, to justify it, you have to prove it worked by showing that youve trained real athletes like Jax (college basketball), Jordan & Gable (college wrestling), Rawley (college/pro football), Baron Corbin (college/pro football), Bliss (gymnastics), and Dana Brooke (fitness). They could have cherry picked the PWG All-Star team of three years ago or New Japans top American guys who have kids and want to be closer to home or Japanese guys who want to be on the international stage, or the fed up with TNA alumni crew, brought them in, without a program. This is not meant as a knock on the program, because it is that program that will keep them on top while New Japan will struggle going forward for not having something remotely similar even though New Japans actual training system is more successful with a higher percentage of recruits.
So he thinks the picks were meant to show that the WWE Perfomance Center is successful at converting athletes into wrestlers.