No solid option ahead of him
The White Sox brought in Paul DeJong in free agency and brought in Nicky Lopez in the Aaron Bummer trade. Neither of those options inspires much confidence at the plate, but both have plenty of experience in the middle infield.
DeJong slashed just .226/.281/.393 over 328 at-bats in 2023. Lopez slashed a similar .231/.326/.307 line in 2023 over 225 at-bats. It's probably the best course of option to have DeJong play against lefties and have Lopez as a utility guy filling in at multiple spots. Montgomery should see the majority of plate appearances against right-handed pitchers in 2024. it might be a different story if there was a solidified starter on the team, but there just isn't.
While Montgomery doesn't have experience at this level, this is the perfect time to give him some. If there was another shortstop ahead of him who warranted keeping him down, it'd make sense to do so. However, that's not the case.