Java and Bedrock do not speak the same language on the wire
The split between the editions is technical, not commercial. Java opens TCP on 25565. Bedrock opens RakNet over UDP on 19132, with an encrypted session tied to the Xbox account. Neither one ever recognises the handshake of the other.
On disk the story repeats itself: the Java world in Anvil files, the Bedrock world in a LevelDB database, with different item identifiers. Migrating between editions is a lossy conversion, not a folder copy.