My guess is that it’s trailer, damaged interpositive footage, or press kit footage, scanned in 1080p. The fact that the footage has damage we’ve not seen in any of the period release prints (including 4K77 or 4K78) or on 1985 IP-derived transfers (e.g., GOUT and JSC) leads me to believe it’s an additional source.
I know it doesn’t have the slight color fringing present on IB techs of the time, but could the source be the mythical Lucas-owned IB Tech?