Actually we’ve run into this too when a custoner has added a new “plus model” to suppliment an original JV300. Even though the machines are almost exactly the same, Mimaki seems to have have neglected converting many of the 720x1080 profiles over to the new model in favor of using 720x1440 instead - not sure why.
If you know someone who has the Mimaki MPM software, you could have them convert you favorite profile from the old JV300 over to the new one.
-Dave M