not true
You can still climb that ladder by facing it all the time and strafe left to get out of it when you've reached the top... and this is usually what I do.
In fact the ladder code works like this:
-if you face the ladder AND your pitch is > to -45 degrees, FORWARD will go UP
-if you face the ladder AND your pitch is < to -45 degrees, FORWARD will go DOWN
-if the ladder is on your left, STRAFE LEFT will go UP (no matter your pitch)
-if the ladder is on your right, STRAFE RIGHT will go UP (no matter your pitch)
-if you have the ladder in the back AND your pitch is > to +45 degrees, FORWARD will go UP
-if you have the ladder in the back AND your pitch is < to +45 degrees, FORWARD will go DOWN
the opposite of the mentioned keys do the opposite movement. When talking about pitch, + means up and - means down (I'm not sure it's like that in the HL engine, actually I think it's the contrary).