Lot's of 1970's bike frames could handle both 27" and 700c wheels and if the right brakes were used they bike could handle either just by moving the brake pads. I have three such bikes. So the manufacturer only had to stock two sizes of rims and possibly different length spokes and then make sure the correct wheels got on the right ships.

That is what makes older bikes so versatile today; they have the clearances to handle skinny tires on lightweight wheels for racing and with just a wheel swap you can go fat and bomb on dirt roads.