Concept: Language with a phonemic distinction between /ɬ/ made by letting air pass over one side of your tongue ('mono') and /ɬ/ made by letting air pass over either side of your tongue ('stereo')

Concept: Language with a phonemic distinction between /ɬ/ made by letting air pass over one side of your tongue ('mono') and /ɬ/ made by letting air pass over either side of your tongue ('stereo')
No joke, the Sto:lo language of Halq'emeylem (indigenous to the land I'm on here) does distinguish between this if I'm remembering correctly.
(I mean its not described as stereo / mono, but the way to do the softer of the two phonemes was described to me as blowing the air out both sides of your tongue)
I got this info from Wikipedia (https://en.m.wikipedia.org/wiki/Halkomelem) so may not be fully accurate, but
if you're thinking of tɬʼ ⟨ƛ̓⟩ and ɬ ⟨ɬ⟩ or lˀ ⟨l̓⟩, the first one is palatal (you put the blade of your tongue on your hard palate) while the other two are coronal (you put the tip of your tongue on your alveolar ridge or teeth), so it doesn't have to do with which side(s) air comes out, but where the obstruction is happening. (not sure how much linguistics you know but /l/ as in lot also involves air going out the side(s) of your tongue)
I think there's very little acoustic difference between "mono" and "stereo" (like little enough that I suspect it's impossible to distinguish for humans) so I'd be very interested to know if there's a natural language that distinguishes them. Do you have any further info?
I think I was thinking of the fricatives marked as x and modified x's, but I will guaranteed mess up any level of detail beyond that. There's a pretty good chance I'm mischaracterizing something about this, so if you're curious to the point of wanting to contact an actual language speaker I might be able to get updated contact info for the guy who worked with my class last year.