var. pratensis was added because of var. angustifolia.

see https://explorer.natureserve.org/Taxon/ELEMENT_GLOBAL.2.130185/Cardamine_pratensis

Now that var. angustifolia. is ranked as Cardamine polemonioides
there's no reason to keep var. pratensis.
Cardamine var. pratensis has to be considered at species rank aswel now

Moreover var. pratensis isn't consider as valid nor a synonym in POWO
https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:45334-2