one reason due to smaller traces because the amount a time of the LEDs are switched on.
that is contradictory, the less time a LED is switched on, the more current is needed to maintain the same intensity

Of course, brightness is a design trade off much like other issues
No it is not it is a design spec, if someone asked me to design a sign (which I am asked on a regular basis) my first question before any design is started would be "what intensity is needed?"

The issue is not that you can get less power, ANY LED design (switched or not) can be made to use less power but that WILL violate the design spec

Anyone can, by ignoring the design spec (in this particular case intensity), "improve" something, but if the customer does not get what he wants what good does it do.

Of course, if you, keeping the current the same, switch a LED on for a shorter time you will use less power, but if nobody can read your feeble sign, what good does it so?

You can not produce "the same" with less "on time" without increasing the "on current".

Erik