Another reason for Sandbox mode: Bugtesting

Maybe it's been suggested before, but it just kind of hit me when I saw a post reporting a bug where Kalista can attack while being suppressed.

Remember that one Thresh bug that plagued Rioter QA Analysts for many months, where Flay would not move the target? And some random player happened to figure it out by happenstance?

How much easier would it have been to figure out the bug in Sandbox mode? Sandbox mode would help long spell cooldown bugs to be diagnosed better (Kalista + suppression bug!!!) Item bugs, spell bugs, etc. Sandbox mode can help get the players more involved, beyond just PBE players.