It hasn't been missed, but when pointed out, those pointing it out were anathematized, new councils were held to 'fix' the leaks. In other words the heresies that were brought forward were merely swept under the rug, hoping people would forget about them.
The fact that they keep being renewed, shows that Yahweh is indeed working in some to bring the truth out. He really doesn't want a soul to be lost:
Ezekiel 18
20 The soul that sinneth, it shall die. The son shall not bear the iniquity of the father, neither shall the father bear the iniquity of the son: the righteousness of the righteous shall be upon him, and the wickedness of the wicked shall be upon him.
21 But if the wicked will turn from all his sins that he hath committed, and keep all my statutes, and do that which is lawful and right, he shall surely live, he shall not die.
22 All his transgressions that he hath committed, they shall not be mentioned unto him: in his righteousness that he hath done he shall live.
23 Have I any pleasure at all that the wicked should die? saith the Lord GOD: and not that he should return from his ways, and live?
24 But when the righteous turneth away from his righteousness, and committeth iniquity, and doeth according to all the abominations that the wicked man doeth, shall he live? All his righteousness that he hath done shall not be mentioned: in his trespass that he hath trespassed, and in his sin that he hath sinned, in them shall he die.
25 Yet ye say, The way of the LORD is not equal. Hear now, O house of Israel; Is not my way equal? are not your ways unequal?
26 When a righteous man turneth away from his righteousness, and committeth iniquity, and dieth in them; for his iniquity that he hath done shall he die.
27 Again, when the wicked man turneth away from his wickedness that he hath committed, and doeth that which is lawful and right, he shall save his soul alive.
28 Because he considereth, and turneth away from all his transgressions that he hath committed, he shall surely live, he shall not die.
29 Yet saith the house of Israel, The way of the LORD is not equal. O house of Israel, are not my ways equal? are not your ways unequal?
30 Therefore I will judge you, O house of Israel, every one according to his ways, saith the Lord GOD. Repent, and turn yourselves from all your transgressions; so iniquity shall not be your ruin.
31 Cast away from you all your transgressions, whereby ye have transgressed; and make you a new heart and a new spirit: for why will ye die, O house of Israel?
32 For I have no pleasure in the death of him that dieth, saith the Lord GOD: wherefore turn yourselves, and live ye.
These verse show Yahweh to be equal and balanced in how He does things. Each person is responsible for their own soul and its eternal life/salvation. They also show that just because one was righteous doesn't mean that person cannot fall away again into unrighteousness. They can. All that is necessary is to repent with a contrite heart and get back on Yahweh's path again.
OSAS is not scripturally true. At least, not according to Yahweh, and that is the God, I listen to, the God of Israel, the God of Abraham, Isaac and Jacob. The God that Yeshua worshipped.
There is only one Jesus that saves. And he looses none that His Father gives to Him