If the average orphaning rate is 1%, then this means that an average block is taking about 6 seconds to propagate (6 sec / 600 sec = 0.01).

This means that a miner's hashing power is being put to good use for 594 sec and wasted for 6 sec. In other words, the miner is 99% efficient at deploying his hash power.

If this miner is a small miner, then that's the end of the story. A small miner essentially never mines two blocks in a row, so he always loses 6 seconds for every block he solved.

A large miner is different. Every once and a while the large miner will solve two blocks in a row. For that second block, the miner didn't have to wait the 6 seconds. In other words, his hash power was deployed 100% efficiently for that block.

A miner who controls 10% of the hash rate will mine two blocks in a row 10% of the time, and so he is 99.1% efficient (assuming 1% orphan rates):

0.9 x 99% + 0.1 * 100% = 99.1%

A miner who controls 30% of the hash rate will mine two blocks in a row 30% of the time, and so he is 99.3% efficient (assuming 1% orphan rates):

0.7 x 99% + 0.3 * 100% = 99.3%