yes, Linksys WRT is one of the few devices, were sysupgrade with factory image works and is required in some cases (factory instead of sysupgrade image is required in the special case of coming from Linksys WRT v19, to properly resize partitions)
but for practical reasons, I would nevertheless wait a few days and keep an eye on forum updates: at least for the larger Linksys WRT editions, people alerted defects in the Linksys WRT specific partition switching in some cases during firmware upgrade: Linksys WRT32x bricked both partitions.
I frankly do not know if the 1900 is also affected, but there is a chance that is partly affected as well.