The cynic in me thinks that might have been them doing a "Scream test" - break something, see if anyone notices (enough), if not, continue with getting rid of it. If it causes a stir, pretend it was just a once off issue.
"Broke" is an overstatement. The post says they only disabled using the API to sell new paid extensions or in-app items. Existing extensions were not affected, except extensions that added brand-new features since March and wanted to charge users separately for them.