Apple has Juneteenth off now, and did so before this announcement.

My (large media) company has had it as well. We've made inclusion and progression a huge point of emphasis over the last decade though, so it's not really surprising.

Why does your labor union allow that?

Most people would prefer an extra vacation day that they can take any day they want, or accumulate and take in a block, over a mandated holiday on a particular day.

Well, check my prediction 1-2 years from now. Your company will give you a day off on both MLK and Juneteenth. On Juneteenth 2023 you'll have a day off (this and next year it falls on the weekend)

The only exception to this would be companies (and schools) that will use Juneteenth as an education day instead of giving the day off. (I hope companies don't do that. If I want to get educated I have books and the Internet)

My company decided to give Juneteenth off this year as a change to the calendar effective from January. Its treated exactly the same as every other federal holiday, if it falls on a Saturday we get Friday off and if it falls on a Sunday we get Monday.

Same. Last year it was a half day, but this year it's a full holiday like any other (observed on Friday, June 18), and I assume will continue going forward.