Templates deliberately classified as "unknown" refers to those templates which we class as "unknown" here at Tardis, even though there may be other types that would fit it better. Indeed, most of these templates are actually "notices" in Wikia's scheme of template classifications. However, because these are all exceptionally smaller, graphical notifications, we want them to appear on pages, even on mobile screens. Thus, we class them as "unknown" to effectively bend the classification system to our will.
Note that we don't do this for every kind of notice that looks like the ones below. In fact, stubs, on which these kind of notices are modelled, are classed as notices. We want stub notices to disappear when not viewed on the desktop. This is because editing from mobile device is a fairly rare occurrence, and we're happy enough to hide the stub templates from the mobile audience that is by and large just reading our articles — not editing them.