In a way it's good that Scholes says stuff like that. For one, he's right; as good as Herrera is, he's not in the elite rung of central midfielders (yet). For another, we already have enough ex-player ambassadors who parrot official club lines, it's good to have a guy who every now again gives a different opinion. And it all comes from someone who cares about the club; whoever he may or may not upset with his comments, he at least says them because he wants the best for United right.
And besides, in Ander's case, he may use it as extra motivation to prove just how good he is. For all we know Scholesey is a master psychologist who knows exactly how to rile players up, in ways that get maximum performance from them