It sounds to me like a product of the ‘90s. CRTs were still common, and they support essentially arbitrary fixed refresh rates. It wouldn’t have been a big deal at the time. It’s like how the original Doom runs at a native 35fps when you don’t use interpolation.

I haven’t played simultrans, but I wonder if it feels less janky on a 120 Hz or 240 Hz monitor, since both of those values are evenly divisible by 40. Compared to playing on a 60 Hz display or other non-multiple of 40 refresh rate monitors.

Came here to say this, was an instant bounce for me.