Yes, I did find that in the rules. Looks like I've been labouring under a misapprehension all these years. I've always assumed this to be true ever since I was told this as a junior, and I'm in my sixties now.
Many years ago, I was told that the tee blocks should always be positioned no closer than two club lengths from the back edge of the teeing area. I was told that this is the only time
time you could tee off in front of the tee blocks, because you are allowed those two club lengths from the back...