Kruser, your going to need to check your rules. If I list just Miller and felix does not pitch my line still gets adjusted. If it was Batista for instance, I would have gone up to at least -130.
You dont get to keep the same line just because you list MILLER. The line changes as soon as you get any new pitcher. Even if its not the one that you list.
ChopTalk's description is, of course, correct.
An easy way to state and remember the rule is that the sportsbook ALWAYS has the RIGHT to change the money line with ANY STARTING PITCHING CHANGE with the exception of LISTING PITCHER(S). LISTING only converts the bet to NO ACTION when there is a change in a starting pitcher.
In MLB, you can NEVER lock in an actual ML for a game that isn't subject to revision on a starting pitching change (except very rarely, it is possible to have no starter specified).
Always check the individual sportsbook's stated rule, because the rule above applies to almost every sportsbook, but not necessarily to ALL sportsbooks.
One reason to LIST only one pitcher is if the other pitcher (the one NOT LISTED) is subject to change, and you trust the sportsbook to make a fair adjustment and want ACTION even if there is a change in the other pitcher. Also, presumably, when the "new" line is available, it may be inconvenient or impossible for you to re-bet it.