We want to keep it this way so people can still make plugins work for older versions of Cura, like 3.6, where the 'api' field with just a single major version, instead of the 'supported_sdk_versions', which can be either a version-string like '7.6.0' or a list of version strings.
The Cura 4.9 release will have expanded functionality. If you have a plug-in that uses this functionality, marking it as using SDK 7.5.0 will notify older Cura releases that they can't use that plug-in.
We're going to repurpose this plug-in to read other file formats as well.
Currently it still only registers itself as PLY file reader. But I'm about to change that.
Contributes to issue CURA-6739.
