It isn't a redefinition. IRIs (or URIs if you prefer) have always encompassed the ability to be things other than http: and https:, and the application has the ability to assign arbitrary meanings to what follows the colon. You just don't see it very often on the web.
I meant the concept of deep linking, which used to mean that you refer to a specific link on a subpage of a site (Such as a particular article), rather than the domain. There's a connotation of legalese to it - The word is/was used as a negatively loaded term by those who think they have a right to control who links to their site/content and how they do so. See also: https://en.wikipedia.org/wiki/Deep_linking