Is it still possible to enroll in BRS?

I was tracking that you only had calendar year 2018 to enroll, however I recently noticed I had the option to enroll on MyPay.

Background: dumb private me thought I was automatically enrolled since I swore in Jan 2018, but it turns out that it goes off my DEP date which was Dec 2017. And neither I nor my first line noticed for like 4-5 years. In 2023 I tried to get my automatic match and discovered I wasn't enrolled.