as far as I can remember from feeling it the seal didn't seem like it was tight enough to be gas tight anyway, you may have found what may be leaky on most turbos ?
unless there is a big build up of carbon or soot around it meaning it may be leaking much worse than normal, as I don't think it was bushed in anyway just a stainless spindle in a hole in the steel chra.
also just visable in the pictures you posted above is the turbine heat shield , sits just below the turbine and extends a few mm out further than turbine tips, that then seats in the vnt ring to seal off the vnt activation ring area from soot /heat.
with you being tuned quite highly as I remember its possible the heat shield could be worn or heat damaged which in turn could lead to more pressure getting to the leaky vnt pin.
I would keep an eye on it for now or speak to a turbo rebuild place about how leaky a new chra would be from that pin.
I cant say ive ever heard of anyone finding this sort of leak, the more frequent is from the join manifold to turbo, or from the manifold to block gasket area.
ps is that your with the egr blanked at the exhaust manifold?
if its not mapped for egr blanked the vnt maps will be holding the vnt vanes more closed for egr purposes and with nowhere to go as blanked that could also be increasing the pressure on the turbine /heat shield and out to control pin.
