Five words: it doesn't work like that.
Teams can't 'hide' their UFA's by signing them on June 21st. Vegas can negotiate with Russell as a UFA during the expansion draft window and if he agrees to sign with them, that becomes their Edmonton selection. IE; Even if he is unsigned he's exposed.
Why would Vegas do that? Well...Russell at, say, 4.25x5 vs...
Benoit 'healthy-scratch-and-never-hit-20-goals' Pouliot
Brandon 'won't-play-a-full-season' Davidson
Patrick 'one-season-till-UFA' Maroon
Tyler '25-years-old-and-49-career-games' Pitlick
...I know who which of the 5 options I'd take if I were them..
Also, doesn't really matter if "all of" player x, y and z are exposed because we only lose one of them. We have 4 high end assets at forward, if we had a 5th it'd be another story but we don't, so protecting 4 and 4 is fine. It's pretty simple, really; if we see Russell as a more important player than any (not all) of Davidson, Maroon, Pouliot, Pitlick, etc., then there's no reason not to sign him ahead of the draft.