The story as told may be inaccurate but it wasn’t simply ‘what we had at the time’ either.

The 74 minute length resulted from Sony rejecting the Philips 60 minute 11.5cm diameter “Pinkeltje” disc size in favor of a 12cm diameter.

It’s quite possible that Sony’s Norio Ohga simply argued that the 9th symphony or various operas fitting would be enough of an advantage for the slight size increase without meaningfully decreasing portability.