I was testing this against both mys2/minw64 and my binaries against PG18 EDB windows shipped. In both cases the selectivity tests fail.

I'm assuming it's a PG18 issue rather than the windows platform, because the tests pass under my PG17 install.

At a glance I think it's because PG18 now includes Buffers in the explain output without needing to specify buffers.

Attached is the idff

pg18regression.diffs.txt