I am trying to ramp up knowledge on SharePoint deployment and usage (never did before), due to a direction to use SharePoint 2010 as a repository platform (wiki format) for our customer's infrastructure documentation.

In my test virtual server, a new site of Enterprise wiki template was setup. Went into Site Actions > Manage Site Features to activate Wiki Page Home Page. The default sub-web then went from /Pages to /SitePages and looks like the default Team template. The odd thing is the Site Actions is missing the New Page option. My colleague does not understand why this is the case, as it ought to be there. The original /Pages sub-web does have the option.

What conditions are in play that influences the appearance of that option?

UPDATE

Another phenomenon observed is in the Site Actions > View All Site Content view, the wiki document libraries listed in the grid will have their hyperlink (e.g. "Site Pages") lead straight to the direct default page. It would not show its own table listing of pages under that document library, unlike the original Pages document library, which expectedly show up as a listing. I wonder if this hints to any problems.