It seems not to be the case. According to SEM (Staatssekretariat für Migration), a B1 oral level and A1 written level at least are required to be granted permanent residency and B1/A2 (oral/written) for naturalisation [1] in one of the four national languages. They do not state the bar to admission.

[1] https://www.sem.admin.ch/sem/de/home/integration-einbuergeru...