It does not prevent all writes, it only prevents protection flag changes, mapping over the region, and unmapping. As far as I understand it, sealed memory might

It does not prevent all writes, it only prevents protection flag changes, mapping over the region, and unmapping. As far as I understand it, sealed memory might even be writable. If the sealed memory is read-only, debuggers and other tools can still patch mseal'ed memory regions using ptrace and similar interfaces.