Have a think about it - secondary turbo doesn't have exhaust routed to it until you 'get on it'. So it (and the secondary downpipe) doesn't get hot.
Any oil residue on the secondary turbine housing / downpipe won't burn off if you're just puttering around town on the primary.
One typical source of oil drips on that side is the IACV (Intake Air Control Valve) which opens and closes the secondary compressor outlet to intercooler pipe. What happens is that blowby collects in the intercooler, drools down the secondary inlet and then dribbles out the IACV butterfly shaft. No big issue, just clean out your intercooler every now and then.
Could be that, or CV grease flicked up from the RHS inner joint onto the downpipe.
I bet if you had a good look around the downpipe you'd find oil residue on it somewhere.
IACV vacuum actuator in green.