Ok checked the datasheet and sure enough it specifies a 21 second typical update time at 25C for an image with no red; images with red are slower.
They apparently sell a "fast update" variant that's 3.8 sec update cycle time and monochrome.
Good to know but not particularly a deal breaker for my use case. It's only going to be used for IP address, version, etc. configuration display and will only update when these change, the system is power cycled, or every 24 hours (manufacturer recommendation to prevent ghosting)