Um, i think that was the old hardlimit for blocks. Some miners did not update that yet. It's no proof that all transactions were cleared at that point in time. It's fully up to the miner how many transactions he want to put into a block.
That's not the hard limit. The 'hard limit' is 1 MB, you're talking about a 750kb soft limit. It is interesting because Antpool was one of those that mined a 749kb block, yet the block that they have previously mined was 930kb.
It would be convenient to check the last blocks and found one of these blocks with only one transaction, the block reward, and believing that it shows the network is greatly underloaded.
If I'm correct that is because of SPV mining.