Mmmm, nono... it X/Y and Rx/Ry are the left and right analog sticks. The drivers report the gamepad as a whole as a single device as far as I know, but technically there are 4 axes that way. X/Y and Rx/Ry are how dual-analog gamepads and Windows handle most any dual-analog setup.
I'm not sure if DOSBox uses them as two separate joysticks, as I don't think I have any 2 joystick supporting games laying around... but still, it's certainly one gamepad with more than 2 buttons, and DOSBox is failing to see it as such.
And why would forcing 4axis fix the 4-button problem? I mean, I set 4axis and all my 4-button games worked entirely as expected. Shouldn't auto have figured that out?
Perhaps it's that I don't know what auto goes looking for...