Choice is not the culprit here, since they are fairly fast and accurate at posting, IME. I'm talking Alamo, for example.

If the WN credits take anywhere from 2 days to 12 weeks to show up, with no way to predict, they play havoc with your CP planning. Since WN doesn't give you anything special for the 101st and more credits in a year, it makes no sense to accumulate/transfer more than 100. If you cut it too fine, you risk not having enough credits post, or too many.

Sometimes you are forced to make an extra transfer (like from Choice, Diners, etc.) when you don't want to, and you waste credits when some unexpectedly show up, or risk having some old ones scroll off. This happened to me last week when my CP deadline was upon me.