Everything @aarongable mentioned in the news posting noted this clause:
For Client Developers, does that mean we generally do not need to worry about updating our clients in the foreseeable future, and it will be acceptable for quite some time to submit an inapplicable/alternative reason (even though LetsEncrypt will ignore it and log the reason in accordance with these new guidelines)? Past actions by ISRG and the goal of continuous automated renewals lead me to believe this interpretation is correct, but I'd like to be sure no actions by developers are necessary.