Why is this an issue?

The information that an enumeration type is actually an enumeration or a set of flags should not be duplicated in its name.

Noncompliant code example

enum FooFlags // Noncompliant
{
    Foo = 1
    Bar = 2
    Baz = 4
}

Compliant solution

enum Foo
{
    Foo = 1
    Bar = 2
    Baz = 4
}