Watermark Of German Early Weimar Period - Misunderstanding By Me?

In the years 1920-1923 two watermarks were mainly used in Germany: The lozenge (Scott wmk 125), and the network or waffles (Scott wmk 126).
In the scans below it seems like there are two sizes for the network, but I can't find anything about it on the internet. What am I doing wrong? Did I fall for optical illusion?

Optical illusion.

The network pattern isn't very sharp (it never is) and the production quality is poor (it always is), resulting in a watermark without a clean pattern.

Your eyes tend to compare the center of each stamp, where the top stamp's watermark pattern is offset from the bottom stamp's pattern by half a cell. This makes the top stamp's cells look shorter than on the bottom stamp, where the watermark is a clean 2 cells tall in the center of the stamp. If you look at the right or left third of the top stamp, you'll see that it's 2 cells tall there as well.

Thanks. Continuing with my eye check.
Here are two examples of the waffle wmk. The one on the left seems to me rounded, like the image in stampworld, and the one on the right seems more like straight lines, like the network pattern shown in Scott.
Am I seeing things again? Another illusion?

very common.

A watermark is created by pressing a shape into the (mostly) wet paper. creating a thinner spot.

So wetter or dryer paper can have an slighty different effect, how hard the watermark was pressed into the paper can have an effect. a slight shift of the paper can have an effect.

Even the color of the stamp can give a slightly different effect

Lots of variables.

Thank you. When do these varieties become worthy of noticing and documenting in catalogs?
Also, what is the real form of this wmk? StampWorld and some other online resources describe this wmk as curvy (stampworld's version is very much like the curvy scan). Scott shows a grid.