I think it all depends on when and what kind of nutes to be exact.

Organic nutes?......No need to flush

Chemical Nutes?.....Flush with about 1 week left.

Ideally, you might consider to stop nutes 3 weeks prior to harvest and allow the plant to use up its store of nutes in both plant and soil, thus mitigating the need to flush at all.

Its not critical to the health of the plant, but can be for the harshness of the smoke