We can see they are serving Krishna and glorifying Krishna. They are not glorifying themselves and talking about themselves.
This is very subtle. Because the desire to be adored and praised, which is subtle sex desire, is there even when the person talks about service to Krishna because the focus is on themselves. How Krishna is working through them. Look at me. Look at what a great devotee I am. Krishna is so great and He is working through me. See me. Praise my service. Praise me. Me. Me. Me.
It can be very subtle.
But if we study the writings, teaching and lectures of the pure devotees we do not see this. The focus is on Krishna. Then automatically the devotee is glorious. They become as good as Krishna and Krishna works through them.
The false ego is very stubborn.
Dear Lord, please free me from this false ego. Let me find the ecstasy of chanting Your Holy Names. Let me find the ecstasy of hearing your pastimes. Let me find the devotees who have developed a taste.