Say you are in a tavern. Spirit Guardians is up. The character hides behind the bar, which is 15' long.
The spirits' presence indicates that the character is somewhere back there, but not exactly where. I'd say they can remain hidden. It might be different if this is in a bare room with only one wingback chair to hide behind.
Also, note that most viewers probably don't know the details of the spell. There are spirits flitting about. Okay. And? If I don't know the spell, I don't necessarily know the relationship between the spirits and the character, so that the spirits don't indicate anything to those who don't recognize they are from that spell.
So... context dependent, I think.