Going a little deeper. I am gonna guess why.... however you grab the string, there is a certain amount of stress you place upon your finger / hand / arm system. Synonymous to that placed upon the bow holding hand, when grasping the bow. There are ways to ergonomically hold or address the string ( or bow) that allows you to use a minimal amount of muscle tension to do it. In the case f holding the bow, bone alignment allows you to more easily, with less strain, hold the bow in the proper position for a shot then... say... holding the bow with the crook of the thumb only and a very bent arm.
For the string hand, if you use the tips of your fingers, as seems best at first glance ( less glove / tab interference) there is an increase in the tension of the hand and also an increased tendency to not hold that hand in the same position with each shot, especially as you get fatigued. A deeper hook, especially one that essentially formed as you address the string and not adjusted afterward as you pull back and anchor, can allow for a more relaxed hold, a more repeatable hold and a smoother release since you are able to just relax the hold instead of physically "releasing". In addition, once you get the hold, you can work on using your arm and back to supply the bulk of the holding power, allowing the hand to simply relax for the release and not move away ( to the side of) from the face or other anchor point at the loose. Often, with a finger tip release, it is more difficult to engage the back and easier to " release" by opening the hand, which can take it away from the face.
I find that there is a vast difference in results between your string hand moving back toward your shoulder, in line with the arrow, at the release and with the hand moving away from the face on a sidewise plane because the back was not very involved or the position of the string hand forced or allowed "release" instead of just letting go.
Very easy to say, sometimes not near as easy to do. With a lot of this, the words and the descriptions are the easy part, while the actions and even understanding the descriptions is the hard part. An example is "using the back". Well of course the back muscles are used. Almost have to be do draw a heavier bow back. BUT... once you get what they are trying to describe, it is a very obvious concept. "Getting it", is not always easy. "Doing it" is also not always easy.
Same can be said for the whole aiming scheme. It is easy.... once you "get it" but it is sometimes difficult to "keep it".
At least..... this is my take on it.