Solemn warning vs Flip

I've had a lot of problems with the rulings of solemn judgment and solemn warning. When I finally think I understand both cards some new scenario pops up which confuses me.


Scenario:

My opponent attacks the Ryko I have in face-down defense position with BLS. I flip it and he/she activates solemn warning which ended up eliminating my ryko without getting it's effect and then continued with attacking me directly.

I know one can do this if I flip summon my monster when Ryko will be eliminated without actually being face-up on the field and therefore not getting the effect. I also know that solemn warning is quick enough to activate in the damage step and can negate the summon of cards like Gorz and Tragoedia.

However since Ryko was flipped due to battle I'm getting a bit uncertain if it's actually allowed to do this?


*eagerly waiting for an answer*

Your opponent cheated. You cannot use Solemn Warning/Judgment to negate the summon a monster that was originally set and flipped face-up during the damage step because this is not treated as a summon.

I see, that certainly is useful to know!
Especially since it has already happened 3-4 times to me.

Thanks!