Flashcard mismatched size

I'm using Flashcards for the first time.

I have 2 cards, each has a picture that's 430x429 for front and back.

I notice that when I flip to the back, the images are larger than viewing the fronts.

I've tried Fullcard vs Centered Image. I've tried Grid vs Stack. I've tried reversing which images are front vs back. The back is larger every time.

Is this normal behaviour or a glitch?