Can only one Pokemon have brilliant aura on screen at a time?

Question

Ok so this is a really dumb question but this intrigued me.

I'm hunting haxorus and I had two at a time on screen. One had brilliant aura and the other did not. I encountered and defeated the brilliant aura haxorus, and after clicking through the message where I got my watts, the other haxorus started glowing with brilliant aura. Unfortunately, I couldn't get a shot with the second haxorus beforehand without the aura, but I do have a clip of getting brilliant aura afterwards here.

I feel like I've seen multiple brilliant aura Pokemon at a time but I could easily be misremembering. So, can only one Pokemon have brilliant aura at a time, can only one of a species have brilliant aura at a time, or is there something else I'm missing entirely? I know this is very niche, but if anyone has any info on why this happened, I would greatly appreciate it!

Answer 1

In a surprising turn of events, I stumbled upon the answer while still hunting haxorus which just still refuses to shine the brilliant method is a fraud I've slaughtered over a thousand of these I have charm I want sleep God help me-

In the event that two Brilliant Pokemon are on screen, the one you are closest two has brilliant aura while the other does not.
I managed to get a brilliant ditto on screen and left it alone and by chance, I managed to get a brilliant haxorus later that I brought nearby. You can see the interaction here where the aura shifts between haxorus and ditto as I get closer to one or when the haxorus starts walking away (ditto's unprecedented aura is hard to see because it's small and surrounded by grass but it is there).

Enjoy this insignificant piece of Sword/Shield mechanics I guess :/