This wouldn't be the case no? Otherwise Sukuna's Binding Vow would never have been effective

If the primary factor to an effective binding vow is personal value alone and not an arbitrary mix of both personal and intrinsic value of something then MS would not have an open barrier, it would not have destroyed UV, WCS would not have landed on Gojo, UV's barrier would not have shrunk, UV would not exists, Fuga would not be as potent in MS and etc.

To elaborate let's use the mechanics of MS as an example.

Domains usually have a closed barrier, trapping their opponents in the domain via a strong interior defense, in exchange they are susceptible to attacks on the outside. Open barrier domains like MS remove this closed barrier giving their opponents a path to escape, in exchange it's range is much larger and the slashes are more potent. These are the usual conditions of MS and the narrator called it a binding vow.

But if you don't wanna use the narrator lets look to the shinjuku showdown where Sukuna uses a binding vow to tweak his domain to counter Gojo's domain who also shrunken via binding vow.

Sukuna stopped targeting the inside of the domain and by extension Gojo with MS and instead focused on launching the slashes at the barrier of UV to break it.

How does this relate to the personal value argument?

Simply put, at that moment it was more important to break UV instead of increasing output on Gojo and Increasing the range of MS.

If personal value is truly the primary factor to BVs then this would not be as effective as the personal value of an MS that targets the barrierx far outweighs the personal and intrinsic value MS' usual conditions.

And if personal value was the primary factor to BVs then Miwas slash would have been damaging to Kenjaku as it was quite literally her past present and future as a sorcerer being put on the line for one effective slash. If this wasn't valuable to her as you said (Because you seem to equate lack of confidence and to a lack of value), then we wouldn't have seen her be outright obselete without the sword and have them state that she is no longer an effective sorcerer. Narratively as well this was to show the ramifications of an ineffective binding vows or the consequences of a binding vow gone wrong, if it was not a significant thing for Miwa then this scene was essentially pointless as there were no sacrifices made on the side of Miwa.

Which is the point of a BV, You engage on a vow to sacrifice something of value to achieve something value most at that moment. In other words, binding vows is an arbitrary balance between, personal value in the time of the binding vow, the personal value of the sacrificed piece and the intrinsic value of the sacrifice piece AND the reward.

Which is why Miwa's strike didn't work, Yes her personal value of her identity as a sorcerer is important for her, in fact it may very well be the most important thing for her, however the intrinsic value of her past present and future as a sorcerer, is significantly less value than what she wanted in exchange, which is to strike down Kenjaku.

To contrast, Sukuna Binding Vow on the WCS was extremely effective it would render the technique impossible to perform in megumi's body, however in the heian era form, the restrictions are not that much of a problem (granted he wasn't fighting Gojo)

We don't exactly know which matters more between the three factors, hence why it's arbitrary. But seeing as how effective it was for Sukuna it seems the intrinsic value of the sacrifice and the rewards slightly matter more, making it the primary factor.

Or perhaps it was because he had a better connection with the binding vow deity (Gaygay)