When querying since 1970, it will be parsed into the UNIX timestamp 0. On the other hand, in caniuse-lite data, release date of unreleased versions are null.

Now, when processing since query, there is a comparison logic:

In JavaScript, null >= 0 will be evaluated to true, which causes unreleased versions will be included in the result when querying since 1970.

I'm not sure whether it's a bug or not. I found this problem when I was implementing since query in browserslist-rs, and currently I implemented this feature/bug as-is: https://github.com/g-plane/browserslist-rs/blob/35ed72f516ab1230d0c102169a9bbe25f493fedb/src/queries/since.rs#L53-L62 .