The USAF is % based on AFSC/MOS when it comes to rank, so if there's a low number of E-6/E-7 promotions, that's going to filter down.
Many of these are pinning on E-5 with ~4 years TIS...I can't help but wonder how prepared for leadership they really are.
Keep in mind, the USAF is test oriented when it comes to promotion, no stratification or boards at this level. So if someone is "good" at testing, that doesn't necessarily equate to good at leadership.