In iTunes Connect, under Activity -> All Builds -> latest build -> App Store File Sizes, I see this message:
TestFlight variants differ from store variants and have smaller sizes.
Why is that the case? What is left out? How representative are the displayed sizes? If the smaller variant works perfectly well in TestFlight, why does Apple distribute a bigger variant in the store?
I could easily imagine TestFlight variants being bigger (less optimization/trimming being done), but smaller seems weird. The guide on App Thinning does not enlighten.