In the FlowExecutionStorage class I read that transactions and continuations does not work together. I disagree with the author of the javadoc commentar that these both things usually don't come together.
Think about a typical "buy" process off an online shop. The user will go through 5 pages to enter all details (and here continuations are really helpful to handle the back button) before he clicks on send. This is only allowed one time in the flow. So a typical candidate for a transaction.

Until now I haven't looked into the given workaround but I would say this is a typical scenario and should be supported "out-of-the box". Am I missing something. Maybe this can be achieved by using subflows?