15d38ea claims that "Game versions can now run mods designed for older major versions (backward compatibility)", which is plainly incorrect - see the documentation.
Simply put, factorio_version must always exactly match the game's major.minor, with the two exceptions being game versions 0.12 and older (where factorio_version did not yet exist) and 1.0 being able to load mods with factorio_version set to 0.18, as 1.0 is mostly just 0.18 and wube wanted to have functional mods on release.
15d38ea claims that "Game versions can now run mods designed for older major versions (backward compatibility)", which is plainly incorrect - see the documentation.
Simply put,
factorio_versionmust always exactly match the game'smajor.minor, with the two exceptions being game versions 0.12 and older (wherefactorio_versiondid not yet exist) and 1.0 being able to load mods withfactorio_versionset to 0.18, as 1.0 is mostly just 0.18 and wube wanted to have functional mods on release.