Custom Tax support on Custom Post Types

Under the question on whether Yarpp supports custom taxonomies in the FAQ it states the following:

(a) have either the show_ui or yarpp_support attribute set to true and
(b) must apply to either the post types post or page or both.

Point b implies that custom taxonomies are not supported on custom post types (they must be on a post or page only), is this correct?

If so, any plans to change this?
Surely many people developing custom post types will create custom taxonomies too.

Many thanks,
Jez.

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