, I think you're confusing an EMS with an EMS.
The one I was talking about, like one by Progressive Industries, checks electricity coming into the RV and only connects if it's proper. It's an Electricity Management System
. It's like a Surge Guard, but with a much better warranty. (1 year as apposed to lifetime repair or replacement)
The EMS you described is an Energy Management System
and is intended to switch off power to heavy amp appliances that could overload the system if others are also on. More needed in 30 amp RVs than in 50 amp ones. If it goes bad it generally just doesn't shut off power.
The EMS by PI or Surge Guard can fail and then not send power through to the transfer switch. Most are hooked up to protect shore power, but occasionally folks also monitor generator input by installing it after the transfer switch, between the ATS and the breaker panel.