Used to run a flooring co years ago and cut down many doors, we had a door saw just for this purpose which you used after an uplift and before laying, never really liked it as you would follow the floor with it but for a trade that needed speed to make money it was a popular way of doing things, I always preferred taking them off but there were times when it was not possible or you would do damage that you were liable for so out came the door saw.
Mark