They've found it 6 seconds before BW but it reached too late; Arrival Time Wednesday, April 1st 2015, 23:52:39
I think this timestamp can be forged by the miner and hence it is not the deciding factor. Different nodes may receive the block notification at different times too...
ANT found that block at 23:52:02 and BW found it at 23:52:08 (6 seconds earlier).
But ANTPool's broadcast was not fast as BW (there could be some problems*) and BW broadcasted it to network before ANT So BW's block was accepted.
*these problems might because of;
- slow internet connection
- connected nodes' slow internet connection etc.
If you're running a mining operation like that you should use other mining pools' nodes.
If ANT had broadcasted that block to the BW, Ghash.io, discusfish etc in the first time it's block would be accepted.