yes, it seems inconsistent. And it actually is, I have to admit.
The fact that a property is inherited does not mean that it is used when inherited.
For example, all svn properties are always inherited, but only the svn:auto-props and svn:global-ignores are used that way. All others, while marked as inherited, are only used on the item they're set.
TSVN shows you what the svn lib (and the command line client) tells it to. You can try the same with the CL client:
$ svn propget svn:ignore --show-inherited-props