It is important to remember the "science" behind singing is ONLY to figure out and understand how the greatest singers were able to do what they did. That does ABSOLUTELY NOT mean you can read the science and know how to sing like they did.
Numerous people write all kinds of "scientific" information of singing and how the voice functions. Much of it is only partly right. Some of it is correct. However, if they do not know the corresponding sounds that go along with the scientific terms it is 10000% utterly useless. Unfortunately, none of them do. At least none that I have come across - and I have heard many of the "top" voice teachers and what they teach. Some know a little and then throw in bad. Some do basically nothing. It is sad.
You have to have studied with someone who could explain the sounds - including the wrong sounds - and what physical function corresponds to those sounds. What is the sound of constriction/glottal closure? People use these terms but have no clue what that sound is when listening to a singer. And the worst part is they think they do. So they address the wrong thing and skip over the very thing they actually are referencing. Moreover, a teacher should also be able to demonstrate the sounds of the old singers. The sound of the great singers, not some other sound that does not have anything to do with the great singers.
Lastly, no one can feel their vocal folds yet I hear these quasi scientists telling students they need to do this or that with their cords. There are no nerve endings in the vocal fold, but these teachers tell students to feel this or that in the cords. That is completely misguided and patently wrong. What they do feel instead, 99% of the time, are constrictive tensions (ironically the very things they cannot hear either). They are trying to feel something in the throat/laryngeal area so they have to grip something. That grip is constriction which blocks vocal efficiency. Then they try to look at what some old singers said such as, "I sing from the throat" or the "coupe de glotte" that Garcia wrote about. They wrongly think that it backs up their ideas. Unfortunately it is a completely lack of knowledge. That is why they cannot sing with a sound in line with the greats. Instead we hear wobbles, light and white toned, no core (voce squillante), no high notes of any value etc. And they cannot figure out why this is. That is why it is imperative that a teacher is evaluated on their results. Period. And before and after results in particular. That shows the effectiveness of a schooling. Not how well they write.