Anyway, I wasn't aware about that case, do you have a link to learn more?
official docs: https://support.cloudflare.com/hc/en-us/articles/200170016-W...
Assuming keys vary [pseudo-]randomly, even the Caesar cipher is a viable protection in this particular case (mass e-mail harvesting).
The only thing email harvester would need is awareness of this and few lines of code. The field even clearly identifies itself!
Source: I wrote a generic web-scraper for these emails several years ago :D
Anyway, I wasn't aware about that case, do you have a link to learn more?