How can clozapine cause sialorrhea as well as dry mouth as side effect at the same time?

how can clozapine cause sialorrhea as well as dry mouth as side effect at the same time ?

Clozapine increases salivation through its muscarinic M4 receptor activation or blockade of alpha2-adrenoceptors, or by causing a distortion in swallowing reflex.

doesn’t it cause M receptor blockage??

Sialorrhea is primarily thought to be due to inability to swallow saliva plus Clozapines M4 or partial agonism also plays a role in increased secretion.

but isn’t there M-Receptor block ?