Yeah, it's coming in v19. How do I know this? Because the instance I previously used decided to update to v19 RC1 despite being a production instance. It has instance blocking in the settings. Lemmy maintainers broke API interoperability for v18 and Boost doesn't support v19 yet, though. I decided I would rather use a different instance on Boost than use the web interface on that instance.
They made a lot of breaky changes to the API since Lemmy is fairly young. Not that project management for Lemmy has exactly been great, but I'm guessing this will become less and less frequent and/or they'll start including a handful of previous versions to ease these transitions.
Not all.. Sometimes it is needed to improve things forward. But most releases do not break API access points. v0.19 is going to be great. Hopefully apps are fast in updating.