Me, I count submittals. I can control those. Either I print, stamp and mail something, or I don't. No one else influences my ability to submit stories to markets.
At some level all of us count acceptances. That's the bell to make the dog drool, at least for me. Acceptances are out of my control, except insofar as they do not occur except after I have sent a submission. There is a direct causal relationship there, providing a necessary but not sufficient condition for the acceptance.
Rejections are, in effect, the same event as acceptances. Think about that for a minute -- it's true. They both fall within the category of "editorial response." In a way, it's unfortunate that we use the word "rejection", because that term carries a lot of emotional and social freight beyond the scope of its narrow, technical meaning within the editorial submissions process. Writing is a very emotional experience for must of us anyway, that we label manuscript non-acceptances as rejections is just another twist of the knife. And of course, there is a direct causal relationship between submissions and rejections.
Publication, however, is almost completely out of your control as a writer. Signing a contract does not induce the market to be printed and distributed (or posted on the appropriate server). There is no direct causality here. And markets move, delay, fold, change for a hundred different reasons.
So to answer my friend's question, if the acceptance pleases them, I would suggest they sign the contract. They could always remarket the story later if the publication fails before printing their work. In our field, it generally takes stories many years to age too badly, and besides that an older story can always be revised or rewritten, so there's no great loss in that proposition.
It seems to me that this might be a way to think about the submissions process which could induce less angst and a more clear perspective to each of us working as writers.
Bonus question: How vigorously do you remarket stories from failed publications? Do you identify them as such?