I'm sorry, but y'all really haven't answered poor hahmth's question. I can't either, but I'd like to rephrase it in an attempt to get an answer to what I think s/he is asking.
OK, let's assume that hahmth is either an IMG or a DO and is thus qualified to contract for a prematch position, that is, it is not illegal or against match rules for him/her to do so.
Let us further assume that s/he has x number of interviews, and is not yet done with all of them.
Now a program offers a prematch position with the stipulation that hahmth must accept right away or the offer expires. hahmth, this would make me very wary. On the other hand, if the offer stays open and you are given the time to see other places and then make up your mind given what you have seen, that is another matter entirely.
Let's face it, if you were to make your theorical ROL and the program that wants to prematch you ends up being your top choice, it seems like you have nothing to lose, right?
This in turn raises the question: could you get shafted in some way by taking this offer--which requires that you withdraw from the match--and then later find out that the program you contracted with is backing out or in some other way reneging on your deal?