Plug-in protector does not even claim to protect from potentially destructive anomalies. Other anomalies require other solutions. Cited is at least one anomaly that a built-in Surge Guard (apparently) does not protect from. An anomaly that is too common and dangerous in campgrounds.
Relevant are anomalies that each device does and does not protect from. A recommendation that does not discuss each with numbers is how scams get promoted. Apparently you want to be told what to believe - do not want to know what is required for an honest recommendations.
Does a built-in Surge Guard report a missing safety ground? That can be a concern. Plug-in protector does nothing useful. In some cases, it has caused fire.