Timer is not suitable for a synchronous operation timeout use case

Title: Timing

Describe the issue:

Please add a note about that Timer is not suitable for a synchronous operation timeout use case.

Suggestions for improvement:

NOTE
===
A timer event can be triggered only after the transaction commit while the timer count-up itself starts right after entering the node (the attached node in case of a bounrary event).

In other words, a timer event is designed for a use case that there is a wait state such as "User Task". If you want to notify a timeout of a synchronous operation without a wait state, a boundary timer event is not suitable.
===