Update Re: Ecolink DW-ZWAVE2.5-ECO Door/Window Sensor (April 30, 2017).
It works!

This after Vera Support applied a "Remote Access Workaround" to my VeraPlus Controller (v1.7.2608).
As explained by Vera Support: A "Remote Access Workaround" for an individual's controller unit is currently (April 30, 2017) required for correct pairing of the Ecolink DW-ZWAVE2.5-ECO Door/Window Sensor to Vera Controllers, and to have the device work properly, until a soon-to-be-released Official Full Support is provided (presumably via a firmware update).
(Thank you, kenhagin, for bringing this concern to light, and Vera Support, for a timely and effective resolution!)