Yeah I think that's fair and they should look into tweaking that. Vlad was bad by several metrics last year so they are probably using those metrics. He also gets penalized for playing 1B, the lowest position on the defensive spectrum. The penalties are probably almost as much as JD Martinez does for DHing. So a below average 1B is worth about the same as a DH, and to be honest that does make sense.
But all fielding metrics should be taken with a grain of salt. I read that Trea Turner's metrics were crap this year and he wondered why. Well he found out that merely playing 4 feet more shallow than he normally does was affecting his numbers. He asked the Dodgers if he could play back a little more, they said yes and his numbers went back to normal. So it's very hard for the numbers to account for positioning it seems.
That number has long puzzled me though.