dev's said they will mine to the current block to where they're currently at. It was for them only and they announced it a month prior to it happening
There has never been any real mining to date on BTG, what you see there are just "GENESIS" block transactions that are inserted in the code at birth of the block-chain.
All is created by scratch the BTG is NOT compatible with existing BTC chain as its 2MB and the BTC is 1M.
At this point even when you get a 'payout' on mining pool "pool.gold" where they show a payout the BGOLDD daemon will still show 'zero' when you use 'bgold-cli getbalance' this is because the testnet software doesn't work, and they don't know how to make it work.