Oh no, they are all different people, they all just look the same and are named Jenny.
Lore-wise, they are just a huge family that all have the same vocation and look near identical (same with nurse joy). Theory-wise, they are all clones of the original officer jenny/nurse joy and are essentially brainwashed from a young age to be the face of the pokemon world, for unknown reasons.
iirc the reason it isn't used still is because even with it being trained by highly skilled professionals, it had some pretty bad biases with race and gender, and was only as accurate as it was with white, male patients.
Plus the publicly released results were fairly cherry picked for their quality.