McDermott got hurt last week, then Reiff got hurt three days ago... both had been surpassed by Sidy Sow and frankly neither was very good. McDermott regressed to who he really is, a backup fit for the practice squad, and Reiff showed his age.
They brought in two tackles, much like they have done with numerous other positions a thousand times before. They're auditioning for one roster spot, backup swing tackle who can be that third guy.
This isn't any different than when the Patriots traded for Korey Cunningham and Jermaine Eluemunor at the exact same time (cutdown day) back in 2019.
They need a backup tackle... they signed Zeke two weeks ago, they needed a backup RB. This is team building.