Does AGA always involve shedding of numerous telogen vellus hairs?

There is nothing in the information given that suggests AGA. However, hair collections are best done in a standardized manner such as a five day wash test. One can’t conclude nor exclude CTE. Other possibilities include acute telogen effluvium. 

You need to see a doctor to tell you the difference between the two on your head. If you are a male, then it is most likely AGA