Too much enging speed is more easily absorbed by the drivetrain and will be less upsetting mid-corner than under shooting the engine speed which can make for more abrupt drivetrain shock and have the same oversteer inducing effect as hitting your brakes mid corner.

The goal with rev matching is smoothness (perfect match) so that you don't upset the line you've chosen or mess with the set the car has taken under heavy suspension loading mid-corner.