"Note that Putin says he'll only "track" US warplanes."

That not what they said.  Per the official communications as posted by The Independent "All kinds of airborne vehicles, including aircraft and UAVs of the international coalition detected to the west of the Euphrates River will be tracked by the Russian SAM systems as air targets" Simply, this means that any aircraft, including drones, from any of the countries considered part of the "coalition" (i.e. Britain, France, Jordan, etc.) would be subject to be targeted should they cross the Euphrates.  Much of this is a result of the US being unwilling to adhere to the cease fire terms drafted by by the "peace" group  that included just about everyone but them back in April.  Like it or not, the US is wrong on this one and is being driven by the old Cold Warriors who haven't figured out that the US has no business butting into every other countrys' affairs.