I think it's actually very private.
Sure the exchange like fixedfloat or similar may rat you out in the first hop.
But once it enters liquid it's pretty private (assuming that there are more then two users 😂). Even amounts are not visible.
Peg out is basically a mixer, so the only way would be time correlation.
you could (and perhaps should) peg out in random amounts and time intervals.
then coinjoin if you are paranoid like me.