Bug? Animation hasn't a linear interpolator

It seems the interpolator by default of the Animation library is not the Linear one. It seems to be "Accelerate-Decelerate". Is it what is expected?

EDIT: I got the same result with various devices and OS. Definitely not linear.

It doesn't set the interpolator. The default one will be used.

Thank you. It is not an issue because I can change it with AnimationPlus but I wanted to be sure that it was not a bug on your side.