[gremy0]

It's not, it's just a pretty standard and well understood UX principle; A couple of simple words is far more likely to be read than a long fluffy sentence. It's just a UX pattern.

It's like saying effective contrast is a dark pattern.

[rmrfrmrf]

I think it goes beyond that. "Well designed" temporary signage needs to look out-of-place and basically intentionally ugly.

Temporary signage that fits into the environment will appear permanent, and thereby ignored by the public.

This is why graphic designers use the terms like "effective" rather than aesthetic terminology to describe their work. Sometimes ugly designs are the most effective.

[inetknght]

A couple of simple words are far less likely to be read if they do not interrupt your automatic muscle memory.

The long sentence likely would not have been ignored if it covered the elevator buttons, forcing you to recognize that the buttons are no longer visible where you expected them to be.