Version 5 supported on Win10 but unsupported as "Preview" on 8.1 and 7?

Is version 5 supported for production use by Microsoft in Win10 but remains in preview status for Win8.1 and Win7?

The “production preview” of WMF5 is supported by Microsoft in production (hence the “production preview” name) until shortly after the “RTM” release later this quarter.

Thank-you Don.