...which I suppose is closely related. The deorbiting satellite burns up because all that potential energy goes into heat because of the ~friction~ [edit: compression, thanks for the correction] that limits it to that low terminal velocity.
Put another way, every kilogram of Starlink spacecraft has as much energy "stored" in it's motion as around 4-5 tons of TNT.
SpaceX says otherwise, see [1]
SpaceX spokesman James Gleeson, when asked about the 10 satellites, said SpaceX is “performing a controlled de-orbit of several first iteration Starlink satellites,” using onboard propulsion.
[1] https://spacenews.com/spacex-launches-fourth-batch-of-starli...
Starlink satellites are pretty well aerodynamically balanced when in their "ducked" orientation, but are not going to be able to overcome aerodynamic torques below 200 km or so, meaning they will be unable to point their thrusters in target directions. At that point, there are still 1-2 days before reentry will occur. Hour-to-hour variability in tropospheric atmospheric density due to solar flux levels and geomagnetic activity means that the precise reentry time will be unpredictable to within a few hours (which equates to anywhere along the ground track of a few orbits).
Now, none of this is an actual problem as they're entirely demisable, but the statement that they can achieve controlled de-orbit is false.