[gentoo-portage-dev] Should IUSE include flags specified in "Built with USE Dependencies"

[Amit Dor-Shifer]

Given the following DEPENDency:
this-flag? (app-misc/foo[that-flag])

The respective ebuild should include 'this-flag' in IUSE.
should it also include 'that-flag'?

The manpage says all USE flags "leveraged" by the ebuild should be 
included in IUSE. I understand this as telling me to include said flag, 
but I'm in-doubt.

Amit