Hello,
On a smart object, we can add and keep a transformation ( Ctrl+T ) and we can reset it ( Right Click > Reset transformation ).
Resetting the transformation is the only way and look if something change is (AFAIK) the only way to see if there is a transformation applied.
With smart object, we can see with icons, if we have a filter/adjustment applied : Smart filters, or a layer style : Effects and of course blending options (icon).
It should be interresting to have an icon (as Smart filters, Effects, and Blending options) to see if any transformation is applied to a smart object. They "keep" them, so they "have to" give that information ?