Question: why these simplify() result give different output?

Why would simplify(t^2*x^2+t^2*y^2)  give  (x^2 + y^2)*t^2 but with seemingly same input except changing `+` to `-` fails now to simplify it?  simplify(t^2*x^2-t^2*y^2) gives t^2*x^2-t^2*y^2

Just trying to understand the logic behind this behavior.

In Mathematica both do simplify as can be seen below, which is what one would expect.

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