v393216 may not be a real public update but rather a versioning ghost —the result of Nintendo’s build server assigning a new integer every compilation. Since v393216 = 3 * 131072 , and 131072 = 2^17 , this could represent an internal epoch: the 3rd major refactor of the netcode after the “Ninji Speedruns” sunset.
The string you provided identifies a specific update version of Super Mario Maker 2 Super Mario Maker 2 -01009B90006DC800--v393216-...