Many people use the word initiation to mean lots of different things. For example some people talk about being “initiated into TM“ meaning they were taught how to do mantra meditation and received a mantra; in Reiki the word “initiation” is used to describe each level of learning. Other groups talk about initiation in terms of being given secret postures or attending a ritual.
Mantras, mudras (postures), mindfulness, breathing techniques, chants, rituals, postures, ideas, visualisations and so on are all fundamentally activities that you do either with your body or with your mind. Initiation is not a doing thing although there is a prescribed process, the process is not the initiation. Initiation is the opening of the crown chakra and the creation of higher consciousness along with the revelation of spiritual light and sound energy.
Because it is an ancient thing then there have been a number of teachers and awareness of initiation exists in many cultures. This means there are many teachers who use the word and some who even perform a ritual or process. But despite the fact that there are about 65 groups claiming to be doing light and sound initiation, the reality is most are ritual and process without the actual substance.
Consider it like this: a person could talk about initiation, they could do the process of initiation on you and you would not be initiated. The reason is simple. Initiation requires the involvement of enlightened higher spiritual beings to be involved and to allow the flow of energy and to create the higher consciousness. Without their involvement there may be process, there may be knowledge but there is no initiation.
Since initiation is accessing spiritual energy you have never accessed before using a consciousness you have never had before via a crown chakra that has never been open before then it becomes easy to understand that mantras, mandalas, words, postures, rituals and the like are not initiation, even if the teacher uses such a word. This is not said to devalue such activities but rather to help the seeker of truth understand that all activity has a limit and it is only via initiation into spiritual light and sound via the cooperation of the higher spiritual beings who support humanity that it is possible.