Mostly the psus of other scopes are hiding under the metal-case, so if they "sing" (not unsual behaviour under no load condition) you probably won´t hear it.
This one here is outside this case mounted.
Got the advantage, it couldn´t stray directly into the circuits, disadvantage sensitive people could hear something.
Sure it´s not nice, maybe siglent could do an exchange of "noisy" psus or let the warranty remain if it will be fixed by customer himself.
Edit see pics