True, there's more of a point to be made for faster lenses for smaller sensors. They need the help in low light, the fast lenses smaller and maybe somewhat cheaper to make and shallow DOF is less of a concern (when it's not wanted).
At some point, for low light performance it becomes a toss, smaller sensor and faster lens or bigger sensor and slower lens. I suppose FF sensor has always been better for low light but we're now at a point where it's also cheaper, considering that used FF cameras a available at low prices now and they can be used with affordable old wide-angle lenses, whereas for small sensors, you're mostly stuck with buying expensive dedicated wide-angles for them.