Suspicious auto-commit logic in BEGIN + (COMMIT | ROLLBACK)

H2 has an undocumented non-standard BEGIN [ WORK | TRANSACTION ] command.
https://github.com/h2database/h2database/blob/6b359b683cd4899f96f42a914cc511b310461c15/h2/src/main/org/h2/command/Parser.java#L1046-L1053
https://github.com/h2database/h2database/blob/6b359b683cd4899f96f42a914cc511b310461c15/h2/src/main/org/h2/command/dml/TransactionCommand.java#L42-L44
Perhaps this command exists for compatibility with some other databases
https://docs.microsoft.com/sql/t-sql/language-elements/begin-transaction-transact-sql?view=sql-server-2017
https://www.ibm.com/support/knowledgecenter/en/SSGU8G_14.1.0/com.ibm.sqls.doc/ids_sqs_0329.htm

The command sets Session.autoCommit to false and Session.autoCommitAtTransactionEnd to true.
https://github.com/h2database/h2database/blob/6b359b683cd4899f96f42a914cc511b310461c15/h2/src/main/org/h2/engine/Session.java#L1462-L1465

COMMIT and ROLLBACK commands set Session.autoCommit to the value of Session.autoCommitAtTransactionEnd (true) and reset Session.autoCommitAtTransactionEnd back to false.
https://github.com/h2database/h2database/blob/6b359b683cd4899f96f42a914cc511b310461c15/h2/src/main/org/h2/engine/Session.java#L700-L703
https://github.com/h2database/h2database/blob/6b359b683cd4899f96f42a914cc511b310461c15/h2/src/main/org/h2/engine/Session.java#L805-L808

It means that combinations of BEGIN WORK + COMMIT WORK or BEGIN TRANSACTION + COMMIT and similar enable the auto-commit in the session uncoditionally. Perhaps they should not enable it if it wasn't enabled before the BEGIN …?

Start with the referenced BEGIN handling in Parser.java and TransactionCommand.java, then trace Session.autoCommit and Session.autoCommitAtTransactionEnd at the referenced Session.java locations. Reproduce BEGIN WORK or BEGIN TRANSACTION followed by COMMIT or ROLLBACK, and verify that the final auto-commit state matches the state before BEGIN rather than being enabled unconditionally.