No you are not, you are saying what Mouser says. Mouser is not the manufacturer.
CREE is the manufacturer and they show that the typical forward voltage is 3.4V and might be as high as the maximum of 4.0V. The minimum voltage is not stated.
If your LEDs are actually 4.0V and you have 3 in series and you use a 12.0V supply then they will be very dim or will not light.
If your LEDs are actually the unknown minimum voltage and you have the current-limiting resistor set for 3.4V LEDs then the LEDs might burn out.
Threfore you must gamble about the LEDs voltage, or measure the LEDs voltage and calculate a suitable current-limiting resistor or use only 2 LEDs in series for each group.