There's nothing wrong with your install, it's just that no one edited the D2SE files to show up to date information (similarly the links for stuff like, "Readme", "About", etc, are out of date.
To edit the D2SE file yourself:
- In your .../MODS/HU_2.1/ folder, open the file "D2SE_SETUP.ini" with a simple editor like Notepad.
- Search for the line starting with "ModMinorVersion=", and after the '=' change the 7 to a 21.
- On the next line down, "ModRevision=", you change the 'b' to an 'a'.
- Save the file and close it.
D2SE should now show that mod as being v1.21a