They currently have 1400 members, out of Alphabet's total 130,000. You can find out more about them at their website: https://www.alphabetworkersunion.org/.
They are, for the most part, not legally recognized and don't (can't) engage in collective bargaining.
Personally I think it went public too early, even with the year of secret organizing. They went public with only 400 people, and undoubtedly much fewer were actually active in organizing. Once the bosses get a sniff of anything going to the media, they can be pretty effective at slowing a unions growth. With such a small percentage of the company, they can't do much. The current growth is also pretty slow, growing by only about 2-300 people in more than a year.