They're right.
Technically, Windows 10 is the same major version as Vista, part of the 6.x series. So yeah, you could call it Windows 8.2. Or Windows Vista 4. Or Windows 6.4.
Microsoft hasn't used actual version numbers for the names of their operating system releases since Windows 3.11. The name of Windows 7, Windows 8, and Windows 10 have been marketing driven--the numbers don't mean anything.