I will assist you further, kich. [mwcard=MW1E02]Block[/mwcard] is a Mandatory that gets revealed during the Avoid Attack Step, and [mwcard=MW1E29]Nullify[/mwcard] is a Mandatory that gets revealed during the Counter Spell Step.
I believe that these are examples of the Magic Rule where specific text overrides general rules and a person still can not voluntarily reveal during a Step or Phase. Otherwise, if we went with your opinion that this possibility allows for ANY enchantment to be revealed during a step or phase, we run back into the problem of how to subdivide steps and phases to prevent people from declaring ANYTHING as an event and completely negating having limitations on when you can reveal. People would be able to call anything an event and reveal at any time.
Even sIKE was against allowing reveals during a step, stating that
"A step is a division of an event, so can not find an event inside of a step."Meanwhile, with Banish, the traps triggering during upkeep aren't really a special occasion. A teleport follows the steps of a Move Action with the exception of skipping the Walls step. This allows for traps to be triggered during the Entering Zone Effects Step when dealing with Banish. Thus, regardless of what phase it is, all traps get revealed during the same step following very specific rules which trump any general rules we may have.
I'm also not certain if a creature returning from banishment would indeed trigger traps. It's not specifically stated that the return trip isn't a Teleport, but page 9 of the Domination rules do say that [mwcard=MWBG1E01]Astral Anchor[/mwcard] can not stop the return trip which creates doubt as to whether or not it meets the requirements for triggering entering zone effects, as detailed on page 9 of the Rules Supplement. Basically "return" does not necessarily mean "teleport". This is something that deserves an official statement.