Neverglade Collector shows up when you look for Maokai. No support followers show up when you look for their champions with the exception of 'Boat' effects (draw the champion). Could it be that Neverglade was at some point intended to be a Maokai Boat? He has the vehicle for it.

A custom tag of "maokai" was added to the card, specifically for searching in deckbuilder. Don't ask why.

But really it was probably done by a designer because these cards work well together. It appears like we stopped doing that after the Rising Tides expansion, except hilariously for the tags "punchman" and "susan"... but I'll let y'all see what cards those are for :)

Enter it into the search bar in the client and find out :)

Yeah, searching across the usage of the field, most of it was on Rising Tides cards. "Improvise" appeared to be a thing on some Rising Tides cards, but was clearly a dev name at the time (since the real Improvise vocab term only game out fairly recently)