Pbe Sign up

"Since our goal is to get the best possible feedback to improve the game, we're looking for players who are highly engaged with League and have proven to be a positive influence in the community. We're also looking for people who give excellent feedback. Visit the PBE page to apply or check the status of your application. Sometimes we look for specific types of players, depending on what we're testing in a given cycle. For instance, if we're about to release a new tanky support champion, we might invite a batch of experienced Leona and Taric players to help us out. If you're accepted for PBE access"

My friend has been signing up for the pbe for about 2-3 years. He's never gotten in any type of trouble with Riot, and he's an adc main. So why has he not been picked yet for pbe testing, especially for a huge adc overhaul? If a Rioter sees this, can you please tell me truthfully if you actually have a system for accepting people into the pbe, or is it just random?