Confused about wifi password length

Today in an idle moment I read the Anova WiFi connectivity issues. Only to find a bazare 18 character limit on password length. Whats interesting is that my Anova is connected on WiFi and has a 32 character password.

Explain!

In addition, you do not want any special characters in your WiFi password and you want your Anova to be on your 2.4 gHz WiFi. This is not just limited to Anova. I have many home automation devices in my home, many of my devices have similar requirements. I have also found that many devices, including the Anova do not like Apple Airport Extreme routers. I have multiple routers in my home so this is not a problem for me but others this is an issue.