If you let the inning play out, then in theory you have a 61% chance of at least one run scoring. If you change things to 1 out, man on 3B you have a 66% chance of at least one run scoring (and therefore tying the game). CLICK THIS LINK for RE Matrix
In practical terms -- that means factoring in the ACTUAL hitter and pitcher, rather than an AVERAGE hitter and pitcher -- Servais didn't like Heredia's chances against Miller, so in his mind it's more like a 40% chance of scoring.
With Seager up, one out, it's more like a 70% chance of scoring the one run and tying it up. (That is all assuming you do not mess up the bunt!)
Good Q. Not saying Servais is right, but that's the thought process. With Boomstick you'd have swung away, but with Heredia's ability to bunt it's probably my preference also, to sacrifice and then grovel the tying run on an out or a lucky single.