Query - assigning metadata in DITA

[mhGLEIF]

"you should not feel locked into using them specifically for audience, platform, or product filtering"

http://www.learningdita.com/topic/lc_conditions_filtering_attributes/

Is it really best practice to "bend" the definitions of these (already very broad) categories?

Given the fact that there's also otherprops which presumably means "anything not fitting audience, platform, or product", shouldn't best practice be more like:

"Try to use these as consistently as possible and if audience, platform, or product don't fit, use otherprops or custom properties".

Otherwise the re-usability of that metadata will be affected, maybe even removed?

About the content of the attributes: should best practice be to have some kind of structured lists? E.g. products/platforms might include "family" of products/platforms, release date and/or version number; audience codes might be based on international standard codes e.g. ISO countries, IANA language codes etc. etc.?