Wow. That's wild. I suspect a lot of folks here without aphantasia are wondering what it even means to "know" something without being able to see (or hear/smell/taste/feel/whatever) it in your head.
I guess I "know my birthday" by virtue of the fact that I hear the words "August 17th" (not my real birthday, but yeah) in my head when I casually wonder what my birthday is.
If I know my birthday is on a Wednesday this year, I can picture a calendar page with the middle square of the third row "highlighted" like The Picard Maneuver was talking about with controlled squares above.
For me, I'm not sure I can imagine "knowing" something without either hearing or seeing (or otherwise sensing via some anlogue of the 5 senses) it in some sense in my head.