Might be a hotfix. E.g., 2.10.14 got an update without changing version number.
Similarly, look how the installer has -2 suggesting that this might be its second and third iteration.
Sure enough, here are the notes in the torrent:
GIMP 2.10.18 Installer for Microsoft Windows - 32 and 64 Bit - Update 2 - Fixes Destroyed image (#231) · Issues · GNOME / gegl · GitLab, which corrupted images once the swap file hit 2 GiB