[XeTeX] bug or feature?

[Karl Berry]

    >   \dorecurse{10000}{ hello {\font\a="[AdobeSongStd-Light.otf]"\a Test.}\par}
    >   \stoptext
    >   requires long time,
    > 
    >   \starttext
    >   \dorecurse{10000}{ hello {\font\a="[AdobeSongStd-Light]"\a Test.}\par}
    >   \stoptext
    >   finishes fast.

    Could this feature be used to solve this problem:
      http://tug.org/pipermail/xetex/2009-February/011989.html
    increase the total number of different fonts one can use. 

I will look into the question of increasing font_max beyond 2000, but it
seems bizarre for [foo.otf] and [foo] to have this difference in
behavior.

Is this also somehow related to AAT vs. OT?