I think its purely because he's looked at as a rotational player because of first team experience, and Diallo/Pellistri are prospects.
People underestimate how conservative managers tend to be. At a club like ours, i think Ten Hag could do with a lot more help - if we really want him using those guys, we should make Elanga unavailable by selling him.
I always feel like the clubs head of youth development, should be a lot more involved in terms of selecting which players actually get a chance to join the first team squad. Modern head coaches aren't actually very good judges of talent - its why LVG was obsessed with Blackett and McNair, and ignored Michael Keane. Keane's had a PL career, while McNair and Blackett have bounced around the Championship and League 1.