This all assumes that the optimal strategy is full propagation. I fear that miners today already have incentives to prohibit propagation in order to induce the exact same conditions that happen during fast block creation.
The problem with holding back is that some other miners might get their block out before you can get yours.
In a low latency network where you have 10% of the network and have just found a block, you have 2 choices.
Hold it back
90% chance someone else hits another block and propagates it (payout 0)
10% chance you win it (payout 2X)
Average: 10% of 2X = 0.2X
Broadcast it
99% chance you win the block (payout 1X)
Average: 99% of 1X = 0.99X
So, broadcasting is optimal.
The problem with a high latency situation is that even if someone else hits the next block, they can't broadcast it fast enough. The key is that when a new block is hit, you can trigger all the rest of the network to build on your block by broadcasting it. If the block rate is to fast, then you don't get the benefit from broadcasting it.