They could have added a bigger fan of course, but it’s a balance between heat input and air movement adding a bigger fan probably wouldn’t of made it much faster because these early dryers were only 4800 W or 25,000 BTUs.
Then there’s the other factor of trying to make the machine not to Noisy there’s already quite a bit of noise from the fan in your 63 dryer and having two fans that size in the dryer might’ve gotten a little loud.
John L