In 10.4 mariadb named symlinks were added to make it possible to run the the tools for MariaDB. For example instead of writing mysql to start the client one can write mariadb, or mariadb-dump instead of mysqldump. More details on what was done in 10.4 can be found in the task
In 10.5 we're taking the next step and flipping the logic, i.e. so that the binaries will actually be named mariadb-something and there will be a symlink for the corresponding mysql command.