Brent here. Here were my thoughts behind it:
There were already questions about sp_Blitz and sp_BlitzIndex here. There's also lots of questions & answers that happen to mention those scripts, but I don't think it's right to tag a question with a script name just because it happens to mention the script. The question needs to be about the script, which these were.
There's an SO meta question about this, and it indicates that yes, it's okay.
I already participate in DBA.se, but I can't monitor every sql-server tag. If people were going to use DBA.se as support for our scripts, I wanted to be here to answer. Like the SO meta answer says, the developers (me, heh) have to have an active presence on the site. Having the tag lets me monitor the questions effectively - I've already started piping 'em into our company Slack room so we can jump in quickly to help.
I want out of Uservoice. We're currently using Uservoice for support, and...it's awful. Terrible. The support requests are private, and that goes against everything I stand for as a community guy and blogger. If I'm going to put work into answering questions for folks, I want the answers to be public and well-SEO'd so that other folks can find the answer faster. I already refuse to answer private SQL Server questions (unless it's a client) - I've been steering people to DBA.se for years, and I realized I should do the same for sp_Blitz questions too.