bhyve: vnc limited to 1920x1080?

[xtouqh at mm.st]

I used the following option for bhyve command:

-s 29,fbuf,rfb=192.168.1.6:8001,wait,w=2560,h=1440

...and got rather confusing error message:

Invalid fbuf emulation option "w"
fbuf: {wait,}{vga=on|io|off,}rfb=<ip>:port{,w=width}{,h=height}
device emulation initialization error: Inappropriate ioctl for device

Had to check the man page/source to find the hardcoded 1920x1080 
limitation -- is there any technical reason for it, or is it just "ought 
to be enough for anybody"?