That's not a great example as its entirely possible for additional content production to be baked into the production pipeline in advance.
Generally speaking the timing of release/announcement for such product is the key.
If its all close to release window (e.g. RE4R) then chances are it was pre-planned as an adjunct to the primary offer; if its announced soon after but the additional content takes months to actually become publicly available (e.g. REVIII) then it says that performance likely exceeded expectation because its evident that their ability to capitalize was delayed due to production limitations.
If however neither is announced, then its evidence that post-release a decision was made to apportion production resources elsewhere.
Well, at least it's received quite decent post-launch support.
Photo Mode added in March, and then multiple QOL features added a week ago.