I think mcv may have meant that the single Microsoft account could give access to both versions.
Currently I believe if you have Mojang account for the Java version, you cannot use that account to access the Bedrock version.
Currently I believe if you have Mojang account for the Java version, you cannot use that account to access the Bedrock version.
What worries me is if this change is a prelude to adding some sort of copy protection to the Java edition (beyond requiring a valid account login before downloading the game or connecting to a server).