I've seen many pages be only designed to be used using
parseGroovyFromPage. Is this something that is deprecated now? you’re probably talking about XWiki Syntax 1.0 but even that was wiki markup not groovy (you had to use <% …. %> ).
No. parseGroovyFromPage loads a whole page of groovy and typically gives an object. That page-content should start with http://nexus.xwiki.org/nexus/service/local/repositories/public/archive/org/x...) and it seems widely used from searching the repositories. (e.g. https://github.com/xwiki-contrib/application-l10n/blob/master/src/main/resou... which calls it on https://github.com/xwiki-contrib/application-l10n/blob/master/src/main/resou...) Should such a source not be as a .groovy file but a .wikipage file?? The <% %> of the XWik syntax 1.0 is for embedding groovy. That's something else.
I've also seen velocity-based content to be the core of the UI of most
applications and be contained in the content of pages. That’s in vm files, not wiki pages. ... and is often embedded in macros. So, in your proposal, any macro code whose biggest part of the code would be between {{velocity}} and {{/velocity}} (as suggested in most tutorials) would not be living in a separate file but within a wiki-page file. Right?
Paul