I want to export mesh data with Alpha point attribute into FBX file to use it in Unity. But somehow Unity seems to ignore Alpha attribute in exported file.

By inspecting some FBX files, I found the following:

1. Value of FBXHeaderExtension.Creator in exported files is always "FBX SDK/FBX Plugins version 2020.0.1" whichever FBX SDK version I choose.
   
2. Some versions of FBX Plugin produce FBX file which contains an attribute named "Alpha" as user data. It also contains Cd attribute of 4 channels.
   
3. Unity works well with FBX files that contain the user data.
   

The issue is the first one. Selecting an FBX Plugin version may not work correctly.
Is this simply a bug? or Do I need to do some additional process e.g. installing another version of FBX plugin separately?

I'm using Houdini Indie ver. 19.5.493, on Windows 10.