When might it be beneficial to have slightly ambiguous language contained in a contract between two companies?
In general, it is not a very good thing to have ambiguity in a contract. Such ambiguity can lead to a great deal of litigation down the road. This is why lawyers (as in this article) strive to remove ambiguity from contracts.
There can be times when ambiguity in a contract is beneficial, at least in the short term. The clearest such time is when the two firms need to come to an agreement quickly and there are still issues about which they are not in total agreement. In such a case, it can be beneficial to "finesse" the issue by putting ambiguous language in the contract and hoping the issue does not come up.
A firm may try to put ambiguous language in a contract as a way of giving itself "wiggle room" to act in a way that is beneficial to it but harmful to the other party. However, this can backfire as courts tend to read ambiguous language in such a way that goes against the interest of the party that offered that language.
Ambiguity, then, is not typically a good thing (in the long term) in a contract.