The new block definitions/aliases for coral and dead corals are thrown as errors in 1.21.0 when used in Add-on component "minecraft:inside_block_notifier": Here is a sampling - Errors are as follows:

[Json][error]-1.21 | actor_definitions | C:/Users/seeit/AppData/Local/Packages/Microsoft.MinecraftUWP_8wekyb3d8bbwe/LocalState/games/com.mojang/development_behavior_packs/Stained_Frames_BP | stained:frame | minecraft:entity | components | minecraft:inside_block_notifier | block_list | 'minecraft:brain_coral_block​' is not a valid block type, and is not being added to InsideBlockNotifierComponent's watch list.

[Json][error]-1.21 | actor_definitions | C:/Users/seeit/AppData/Local/Packages/Microsoft.MinecraftUWP_8wekyb3d8bbwe/LocalState/games/com.mojang/development_behavior_packs/Stained_Frames_BP | stained:frame | minecraft:entity | components | minecraft:inside_block_notifier | block_list | 'minecraft:bubble_coral_block​' is not a valid block type, and is not being added to InsideBlockNotifierComponent's watch list.

[Json][error]-1.21 | actor_definitions | C:/Users/seeit/AppData/Local/Packages/Microsoft.MinecraftUWP_8wekyb3d8bbwe/LocalState/games/com.mojang/development_behavior_packs/Stained_Frames_BP | stained:frame | minecraft:entity | components | minecraft:inside_block_notifier | block_list | 'minecraft:fire_coral_block​' is not a valid block type, and is not being added to InsideBlockNotifierComponent's watch list.

[Json][error]-1.21 | actor_definitions | C:/Users/seeit/AppData/Local/Packages/Microsoft.MinecraftUWP_8wekyb3d8bbwe/LocalState/games/com.mojang/development_behavior_packs/Stained_Frames_BP | stained:frame | minecraft:entity | components | minecraft:inside_block_notifier | block_list | 'minecraft:dead_brain_coral_block​' is not a valid block type, and is not being added to InsideBlockNotifierComponent's watch list.

[Json][error]-1.21 | actor_definitions | C:/Users/seeit/AppData/Local/Packages/Microsoft.MinecraftUWP_8wekyb3d8bbwe/LocalState/games/com.mojang/development_behavior_packs/Stained_Frames_BP | stained:frame | minecraft:entity | components | minecraft:inside_block_notifier | block_list | 'minecraft:dead_bubble_coral_block​' is not a valid block type, and is not being added to InsideBlockNotifierComponent's watch list.

[Json][error]-1.21 | actor_definitions | C:/Users/seeit/AppData/Local/Packages/Microsoft.MinecraftUWP_8wekyb3d8bbwe/LocalState/games/com.mojang/development_behavior_packs/Stained_Frames_BP | stained:frame | minecraft:entity | components | minecraft:inside_block_notifier | block_list | 'minecraft:dead_fire_coral_block​' is not a valid block type, and is not being added to InsideBlockNotifierComponent's watch list.

To recreate: any entity, add "minecraft:inside_block_notifier" to components, formatted for the new named coral blocks, throw errors.