That's the thing. The "existence" of a global symbol isn't observable. Think of `Symbol.for("foo")` as if it were the string "foo". The string "foo" is also gl

That's the thing. The "existence" of a global symbol isn't observable. Think of `Symbol.for("foo")` as if it were the string "foo". The string "foo" is also global, when passed across iframe boundaries it still retains its meaning. One can use this string on either side. Using it doesn't observably instantiate some global flag, though internally there may be interning and whatnot. Similarly, using Symbol.for("foo") doesn't instantiate any flag, observably.