Generally speaking, responsible stewardship of a service involves a tail of wind-down and end of life support. It gives time for people to adjust to new services and/or set-ups, troubleshoot the transitions, and provide some lingering support while the service is deprecated.

As another example, Christian was willing to try to find a way to make Reddit's new API pricing work, but would likely need a good amount of time (say, maybe 6-8~ months of notice) to be able to refactor the application to minimize API calls, trial out new subscription tiers, and figure out what to do for the lifetime users. Instead, he got 30~ days of advance notice after repeated promises that the pricing would not be like Twitter (a lie) and/or no major changes to the API in 2023 (also a lie).

At the end of the day, the people leading these efforts want to end on a good note so they can point to their work as an example of their skills for future opportunities. It is not a good look, where in the face of a belligerent collaborator (i.e. Reddit leadership), one responds in a belligerent manner. Even if Reddit leadership is well deserving of scorn, responding in kind does not create a great professional image.

BotDefense (and many other third party tools) for Reddit were built for its community members, not for Reddit the corporation, which is to say the "client" here are Reddit moderators and community members. In that regard, the developers are adopting good practices for their primary clientele.