Your source confirms after Wall's 4th year of college on August 15, 2020, he's a UFA (or could be redrafted?).

Vesey played 4 full years of college hockey. Unlike Wall who's only completed 3 years of college hockey. Wall will have completed his 4th year of college hockey on August 15, 2020.

After rereading that I think I was mistaken and you are right. But in college sports you only get 4 years of eligibility and since he is in his 4th season with Umass-Lowell. So could August 15, 2020 be the date he is free to sign wherever he wants?

Regardless of you mixing up the date that Wall becomes a UFA if unsigned, you bring up a great point that Wall could sign with any team after August 15, "2020". Looking at the Rangers goalie depth chart, Wall has Shesterken, Geogiev, or Lundqvist (if he doesn't retire and either Shesterken or Georgiev are traded) and Huska, ahead of him on the depth chart. As well as 2018 2nd round pick (39th overall) Olof Lindbom soon to be in the mix. Wall probably figures he's got a much better path to the NHL if he signs with pretty much any other team. Considering the point you brought up about Wall soon to become a UFA, Rangers really must trade him at this years trade deadline or highly risk likely losing him for nothing.