I don't work directly with PLCs but we do have them at my work. The main thing that makes these different from any other devices is that they typically control physical machines. Which means there is a real danger that them becoming compromised could lead to damaged equipment or even death.
Additionally, many PLCs use older OS versions like xp because their software is notoriously out of date (if it's working why rewrite it when that could introduce safety concerns)
This "urgent" message from CISA does not prove that any of these devices are internet accessible just that if they are then they should be removed. If CISA wanted to require this then they would have released a binding operational directive (BOD) or an emergency directive (ED). Both of which are publicly viewable on their site.
The combination of not giving kids independence then complaining how teens and young adults are dependant on their parents is diabolical.
I often look at the independence that kids and teens are given in other countries and wish that I could have been given that sort of a childhood. I seriously think I wouldn't be as socially inept as I am today if I had that.