PDF question about FontDescriptor

[Helmar]

Hi,

I'm curious - why every Font needs an own FontDescriptor with
Ghostscript, even if it can be assumed to be the same for different
character ranges of the same included TTF-file?

I want to have one font (say /F1T0) with WinAnsiEncoding and another
one (say /F1T1) that has some other characters of the font included.
Both should point to the same binary TrueType-font.

With Ghostscript (and only Ghostscript afaik), I've to make two times
something like
xyz 0 obj
<<
  /Type /FontDescriptor
  ...
>>

Why? Is there a point in the standard that forbids to use same
FontDescriptor dictionary for two different Fonts?

Thanks,
-Helmar