>This is mostly for legacy reasons as search predates the concept of special pages.

>However, would it make sense to instead count these as page views for 'Special:Search'?

One thing worth clarifying is that analytics team doesn't own the pageview definition (https://meta.wikimedia.org/wiki/Research:Page_view), we implement it to the best of our ability. Deciding what constitutes a pageview for search falls on the search team as they are the ones that know their functionality best (substitute "search team" by "some entity with knowledge of mediawiki's search abilities") According to Timo's comment it seems that "?search" requests should be counted as true pageviews but let us know otherwise via phab ticket or this list.