Low attenuating yeasts are low attenuating - in a beer wort. Their performance in a cider, which has a different mix of sugars, will be completely different.
Usually, low attenuation in a yest is related to its ability to eat more complex sugars. Juice is generally made from almost exclusively simple sugars and in my experience even a yeast that is a poor attenuator in beer will chew right through a juice and leave it dry.
Having said that, I've never used Windsor in a cider so give it a go.
Cheers
Dave