Correction: It would mimic an f4-5.6 zoom on a m43 or an f5.6-8 on an APS-C. The 2/3" is ~4x crop, IIRC.
technically, you are right.
However, given the slight extra reach of the x10, it would have a little more bg blur at the long end vs the kit lenses on either. the x10 is 28.4mm f2.8 at the long end which gives just over 10mm aperture. That's bigger than 55mm f5.6 or 42mm f5.6. In my experience, the physical aperture size is a great predictor of bg blur regardless of sensor size. At the wide end, you are right, but honestly none of these kit lenses on any camera has much DOF control unless you get close with the lens near full zoom. The x10 (and Oly XZ-1) should be at least as good as the kit lenses there.

I would almost rather shell out more for an X100 at that price.

