EZEE-1421 allows to overwrite some settings for existing block types. One of those settings was availability of the block types. If the developer hides existing block types (which is already used in the Landing Pages) it breaks LP editor completely. EZEE-1441 was our initial attempt to fix the issue. Given that we are not able to fix it properly due to code freeze we are forced to disallow hiding blocks via YAML.

Proper solution will be delivered with EZEE-1441 in the 1.10 release.