... I am not unsympathetic ...
Fixed that double negative for ya Jay...
Learn English. A rhetorical double negative is not infrequently used to convey subtle shades of meaning that the simple positive does not. For example, substituting “frequently” into the preceding sentence makes it wrong. It is not
frequently used—but it is not infrequently used, either.
A bit harsh, maybe, definitely not called for, imho.
As to the point in hand...it does, indeed, happen...for example in the "Billionaire" series there is one repeated key phrase: "I am not uncertain".
That was some kind of signal between involved parties that some things are happening for sure.
It (double negative) feels like a stronger statement, but I am not sure why.