Hiring freeze means no backfill?

If it is in placed, does that mean if a billet becomes vacant due to resignation, retirement, or whatever, the govt can’t hire a replacement? If a supervisor retired, then employees won’t have a supervisor due to hiring freeze. Or can they promote an existing billet to become a supervisor and swap it out. Based on the link below, it doesn’t seem to allow merit based internal promotion 🥲 unless it is exempt

2017 hiring freeze FAQ