[m-ou-se]

Dutch license plates have similar properties. Not by changing the proportions of the letters, but by cutting out parts of letters. For example, the R is missing a piece so you can't make it from a P and some black tape: https://commons.m.wikimedia.org/wiki/File:Netherlands_licens...

[megapatch]

One could also use white tape as well...

[et2o]

They address this in the article, pointing out that white tape would look different under headlights from the reflective background paint.

[IshKebab]

I'm pretty sure you can get retroreflective white tape. Extra effort though.

[faceplanted]

I believe "extra effort though" is entirely the point.