My question is: if arriving in the last 10 min of a TEMPO in a TTF (no 30 min buffer) is only 10 min holding fuel or full 60 min holding fuel required?
If you think in big aeroplane/long range operations, they may have this fuel loaded as the normal contingency. Contingency fuel once dispatched can be used at any time, but does not need to be available all the time.
Planning, and in flight are two different scenarios. No additional fuel may be required, even SYD hold fuel.
A lot of people approach these questions like they are flying a C172 on a 1hr flight, where you may need to add fuel to reach this requirement. Even a PER-SYD on a narrow body I would not be surprised if their contingency fuel exceeded that requirement.