Yes, but you also need a jailbreak with nonce override (checkra1n does NOT work on A12). This is why downgrading modern iPhones is nearly impossible despite SHSH hosts.
There are four primary reasons advanced iOS users rely on an SHSH Host:
Advanced resellers use SHSH Host services to pre-save blobs for devices before selling them, allowing the buyer to downgrade later.
An SHSH host is any server that can respond to a device’s TSS requests with SHSH blobs during restore/restore-like operations. Normally, when iTunes (or Finder) restores a device, it contacts Apple’s TSS server (gs.apple.com) to request a signed blob. An SHSH host can mimic or intercept that request and supply saved/custom SHSH blobs instead of letting the device reach Apple’s servers. This enables downgrading or restoring to unsigned iOS versions when used with other tools and device-specific exploits.