I belong to some classical singer boards and blogs and this question comes up frequently. A young singer goes to a new teacher or a new coach and is told that they are some different kind of voice than they thought they were. Or the singer is upset that different people put the voice into different Fachs at the same time.
This is especially a problem for someone who is adept at making a variety of sounds, and can imitate well. Someone like this is susceptible to suggestion and may make their voice sound a certain way to fulfill expectations from within and without about how it should be. If they go down that road, they lose out on learning about the possibilities that their own voice can show them about where it wants to go, and how it wants to sound.
This gets to the heart of a functional approach to vocal study. See what a voice is able to do, in which functional ways it can grow, then assess. That is contrary to the idea of getting a voice to a passable state, assessing its future Fach, then developing only the capabilities usually associated with the label. As a voice continues to grow in ability (size may or may not grow), then a possible Fach label might be applied, but because a voice can be in a continual state of becoming (not a bad thing!), one Fach may not make sense for a lifetime, and at any ONE time a singer may straddle Fachs due to a combination of capabilities unique to that person.
Every classical singer must develop clear vowels, dynamic control, a wide range of pitches, the ability to move, and maximized resonance. It takes time to build these abilities, and it takes time for a voice to mature. Fachs are handy general containers for working professionals, but are not as useful for others. Work on your ability to sing first, and let the labeling come much later. Putting “Soprano” on the top of your resume with a list of works performed, along with your live audition, will give audition committees enough information to determine how they might want to employ you. After being cast in several roles, a Fach may emerge, or it might not.
Believe in the process of vocal development over a lifetime. That is the important thing. A free, strong voice will show you where it wants to go.