It definitely is a bit confusing, I'd agree with you there — I'll try to explain it:
Put shortly, this is the exact same company that YC invested in back in S18. The product may be different, but the underlying company (in the legal sense) is the same.
When a startup pivots, they usually have two options: 1. shut down the company, return money to investors, and start afresh; or 2. continue with the same company, just with a different product. You'll hear varying opinions on the "right" way to approach it, but in general, YC startups usually take the latter option as YC is generally of the mindset of investing in the founders rather than the idea.
This is why Retool, Brex, Segment, GOAT, etc. are considered YC companies, despite completely changing what they were working on (the latter two substantially after demo day).