Here is a further summary of the state of the Core/Strategic definition discussion as I see it as of Jan 20. I've split these uses out since they seem less urgent than Annual Planning.
The second identified use for this distinction is for individual team self analysis. Eight teams participated in a pilot in 2015 to try and measure maintenance versus new functionality, and we came up with about ten different definitions, such as planned vs interrupt or quarterly goal vs other. Five teams produced data over a sample period, all by different methods and definitions, suggesting that there is no common, self-evident way to do this at WMF. Teams that are getting value out of this tracking are welcome to continue, but this data can't be matched to the Annual Planning definitions and can't be aggregated for any purpose.
The third identified type of use is for reporting external to WMF, such as the IRS, grants, charity ratings, etc. Each of those uses has distinct and separate definitions, so I doubt any of the Core/Strategic distinctions we are making for Annual Planning or team self-tracking could be used as-is. Whatever processes WMF uses to currently report these things will presumably continue as-is, with teams trusting them to glean information from Core vs Strategic plans at their discretion.