The dissolution of vows at the gate

In simple terms, the dissolution of vows is just a clarification that there is indeed a door, but it is not necessary for the actual dissolution. But in practice, the Torah law is that a vow is not permitted without an act of dissolution, meaning that the action of the sage has a founding status. You ask why this is so. The question is a good one, and Mahrita 69 already addressed it and stated in the name of his father (the Meitet) that the need for absolution is only from the rabbis. In the name of the entire discussion. But I think it can be settled more broadly. In my opinion, the opening that is being discussed in the laws of absolution of vows is an opening, that is, not an absolute consideration. If it is completely clear that this vow was not intended at all from the beginning, then perhaps it is automatically null and void even without absolution. Opening and absolution are required when the opening is not unambiguous. There are opinions that both repentance and not only opening are required. And further evidence is that there is an opinion that migs geis, that is, the vow has expired and is no longer valid, and that it has become clear that it never existed (and this is how Rabbi Shkob also studies the Gemara that states that a vow is something that is permissible in vows n. From this we see that the vow is not nullified retroactively but migs geis, from here on in retroactively). Regarding kiddushin, where there is a clear consideration that the adatah was not sanctified, the kiddushin is indeed invalid (although the poskim usually deny this law, due to the presumption of a positive result). But here too, opening the door is not enough (and certainly not repentance), but absolute and clear consideration is needed.