White noise is not flat on the freq spectrum

So a bit of background, i am trying to make guitar cab impulse responses, and i recognize that when i do AB tests, the actual recorded audio from the sm57 itself sounds a bit brighter, despite not clipping the white noise when making the impulse

So after doing some digging, i noticed that white noise is supposed to make a flat frequency response, but FL is showing that the frequency more like this

https://imgur.com/a/aqIwS6X

if this is true, the white noise curving towards the top end is messing with my IRs. How do i get white noise that is COMPLETELY FLAT?