Every machine is different. Your 1/4 inch foot was 1/4 to whoever measured it on the machine it was made for. Manufacturing tolerances play a part too. If your machine has an adjustable needle you may be able to get a true 1/4 inch that way.
My machine is an old one so right now I use tape on the bed of my machine but that's coming off soon. It will be replaced with a fabric guide that screws to the bed of the machine.
Rodney