Seizing the yacht would be perfectly compatible with a strict anti-extradition stance as long as the seizure is ordered by a Hong Kong court and the yacht isn't

Seizing the yacht would be perfectly compatible with a strict anti-extradition stance as long as the seizure is ordered by a Hong Kong court and the yacht isn't extradited to another country afterwards. There's no double-standard, just a different standard: if something is a crime under Hong Kong law if you do it in Hong Kong, it should also be a crime under Hong Kong law if you do it somewhere else, and be punished as adjugated by a Hong Kong court.