Hi @seanrnicholson
Thanks for the comment.
This is a very important topic, and one that I am happy to discuss openly. Yes, the ACF plugin is currently marked as “tested up to 4.9”, however, it can be used with WP5.0+.
The reason why I have been reluctant to change the “Tested” version is an honest one. I don’t believe that ACF is working well enough in WP5.0 to receive this “tick of approval”.
Due to the many changes introduced by the new block based edit screen, some of ACF’s functionality is left limping such as validation, dynamic metaboxes and styling.
Unfortunately, I am not able to fix these issues without help from the WP team to address various bugs / limitations with the new JS API. So, for now, please consider ACF as “working”, but not “working perfectly” with 5.0.
It may be some time until ACF can integrate fully into Gutenberg, but until then, please consider using the Classic Editor plugin as a temporary solution whilst the WP team iron out remaining issues and better integrate Gutenberg into the existing WP core.
Thanks again for your support, and for developing with ACF!