The pseudonymous but well-connected 'swiftonsecurity' twitter account reports on background that 'RCE' chatter about this particular vulnerability does indeed relate to compromised software update channels. (Not just AuthentiCode, but also MITM on, say, connections to the npm package server.) See
https://twitter.com/SwiftOnSecurity/status/12171594348808478...That said, this same patch set also has a separate pre-auth RCE on Microsoft's Remote Desktop Gateway, which has been documented as CVE-2020-0609 (not ...-0601). See https://www.kb.cert.org/vuls/id/491944/