OP is asking about arrondissements, not suburbs. Arrondissements are a subdivision inside Paris, and they do have their own mayor. But they have less power, it’s more of an administrative position. 50 years ago they were selected by the state, not elected, then the position of mayor of Paris was created, so the position for the arrondissements is more of a leftover of shifting things around.

But your post does answer why Paris can actually make those changes, yes. And no, the arrondissement mayors don’t make those decisions.