It is very hard to create standards when no one is willing to make them. Without an organizing body taking charge of such a task, it is impossible. Individual teachers of singing cannot, alone, do this, no matter how much credibility they may have. In order to establish a “method” or approach, a governing body must examine it to see if it fits into a basic paradigm of acceptability. An individual singing teacher can provide information they personally feel is important for singing teachers to have, but only an objective group of individuals who have the best interests of the largest group of people at heart, and the long term value of the profession in mind, can set appropriate guidelines about what is and is not useful in vocal training for singing.
The profession of teaching singing goes back about two hundred years (give or take). It is therefore older than Speech Language Pathology and certainly much older than “laryngology” as a speciality in the medical profession. It has no criteria, however, as do the other two disciplines, to guide it, and that is most unfortunate.
Of course, ASHA has guidelines for Speech Language Pathologists and the AMA for medical doctors, and have had them for quite some number of decades. The licensure process would not be possible if those guidelines didn’t exist. The early pioneers who decided what was and was not necessary surely disagreed but finally, with the greater good in mind, came to a consensus, at least minimally as a way to begin.  Standards are updated and evaluated on-goingly.
It is very difficult to measure a method or approach without objective evaluation insofar as how it compares to vocal health knowledge, clinical function of the mechanism at a basic level (healthy speech) and what kinds of criteria are considered “normal” in, minimally, classical singing, music theater and jazz. This is not impossible to do. We decoded the human genome, right? It requires only will and determination, but these are things the profession of teaching singing simply does not have. It is willing to tolerate all manner of nonsense under the guise of “artistic expression” even when the teacher of same doesn’t him or herself sing well and when the method advocates something that makes no sense or is perhaps even harmful.
Those individuals who criticize any method that seems potentially harmful or dangerous are regarded as being “jealous”, “angry”, or “pushy” because they are lone wolves. Even if the points raised are valid, and students of singing are either wasting their time or possibly being harmed, individuals who speak out are not appreciated. They are often reviled.
If that were true in the other professions, there would be no “boards” to discipline practitioners who have violated the codes of ethics.  As teachers of singing, if we accept everything everyone does just because it is “well-organized”, or “well-intentioned” or “artistic”, and do not evaluate anything because “it might work”,  the entire profession continues to be stuck in the 18th century.
Let the people who “teach” based entirely on creativity be called coaches, guides, muses or something else. Let the term “teaching of singing” really mean something. If not now, when?