World of Warcraft now supports 4 .toc files for add-ons :
AddonName-Mainline.toc for WoW Retail
AddonName-BCC.toc for WoW Burning Crusade Classic
AddonName-Classic.toc for WoW Classic Era
and still AddonName.toc as fallback if there is no matching version-specific .toc file
This allow add-on developers to release a single package that works on all 3 current WoW versions instead of one release per WoW version.
More details here : https://github.com/Stanzilla/WoWUIBugs/issues/68#issuecomment-830351390
Even if, for a single file, the CurseForge website allows to manually set a different version number for each version of WoW, only the Interface number within the main AddonName.toc file is used by the API to determine the actual game version.
This feature has been released in WoW since june and it's still not supported by the CurseForge API, forcing add-on developers to post duplicate releases for each WoW version as a workaround.
When performing an add-on search using the API for a specific WoW version, the Interface version should be retreived from it's specific .toc file or from the default .toc if the specific one doesn't exist.
In addition, when a new add-on file is imported, the proper WoW versions should be set on the website as well.