All the "wait until the temp needle moves" is just CYA for the "not the sharpest crayons in the box" people. If it isn't in there "those people" will start up and hit full throttle within seconds. Then they will complain "There wasn't anything that said I couldn't use full throttle immediately". The admonition to wait for the temp needle to move now ensures that "those people" will have to wait a few minutes.
The rest of us realize that taking it slow for the first few minutes will accomplish the same thing as idling for 10-15 minutes.