Does the growth of Ahmadiyya prove that they are truthful?

One of those most common counter argument we get from Ahmadis is the following:

“The fact that we’re still growing and haven’t extant proves that we’re a true Jamaat.”

By that standard every religion that is still “growing” proves itself to be righteous.

The Ismailies for example have existed from an earlier time than the AMJ itself. The Ismailies first originated in 1850’s in Iran. Coincidentally, they also recite the kalima and believe God is one, they also believe Muhammad (saw)  is the last and final prophet sent to mankind. 

The Sunnis, the Shias, the Sufis as being the prominent sects of Islam are also growing. How does one prove what sect or religion is righteous by your invented criteria? 

The Hindus have also grown massively over the last decades, perhaps, they have also been proven as righteous by this standard criteria? In fact, most of the religions that stem from 100s of years before still exist till today.