If selection committee considers a specialist, I imagine that the specialist should have medal potential.
From the list of Jones, Blakely, Biles, Wong, Chiles, it is very unlikely that Blakely, Wong, Chiles will even qualify for the UB final. Biles may qualify if she hits all her handstands and delivers a very clean routine. Miller will surely qualify if she just hits, and she has a decent chance to medal given her difficulty and consistency this year. Miller also provides a 0.5 cushion from Blakely’s 5.9D bars which is not small.
At least for beam, Biles and Blakely are anticipated to qualify for the BB final. After that, Roberson or others can step up for the team final. The deficit is just about 0.2 from Lee’s beam routine, and beam is an unpredictable event. Miller’s bars consistency and higher expected cushion will justify a specialist spot.