Frege makes the point that the being of a proposition cannot be identical to its being true. This I find obvious. There are true propositions and there are false propositions. Therefore, for propositions (the senses of context-free declarative sentences) it cannot be the case that to be = to be true. Furthermore, a given proposition that is contingently true is possibly such as not to be true, whence it follows that its being and its being true cannot be identical. (Whether Frege does or would give the second argument, I don't know; but I think it is correct.)
As Frege puts its, "The being of a thought [Gedanke, proposition] thus does not consist in its being true." (Near the beginning of his essay, "Negation.") One can grasp a proposition without knowing whether or not it is true. To grasp a proposition is not to accept it as true, to reject it as false, or to suspend judgment as to its truth-value. To grasp a proposition is merely to have it before one's mind, to understand it. A Fregean proposition is a sense, and no such propositional sense has as part of its sense its being true. That's Frege's point and it strikes me as rock-solid.
Our London sparring-partner Ed now demonstrates that he still does not understand what a truth-maker is:
I wonder if a ‘truthmaker’ as understood by the advocates of truthmaking is the same sort of thing as Frege’s marvelous but impossible thought. Something that if we perceived it for what it was, would simultaneously communicate to us the truth of what it includes.
Ed is obviously confusing truth-bearers such as Fregean propositions with truth-makers. Truth-bearers are representations; truth-makers are not. That's one difference. Truth-bearers are either true or false; truth-makers are not since, not being representations, they cannot be said to be true, nor can they be said to be false. That's a second difference. Truth-bearers are 'bipolar,' either true or false; truth-makers are 'unipolar': all of them obtain. That's a third difference. Truth-bearers are such that their being or existence does not entail their being true; truth-makers are such that their being or existence does entail their obtaining. I am assuming that truth-makers are facts. If a fact obtains then it exists; there are no non-obtaining facts. That's a fourth difference.
There is no point in criticizing a doctrine one misrepresents. First represent it fairly, then lodge objections. And as I have said, there are reasonable objections one can bring.
So far Ed has not lodged one clear objection.