In this case it might be that the mempool.space node received the block 826743 before the block 826742 because there is no way that the block 826743 would have been mined before the 826742 because the latter needs the block header of the former. The real mined time isn’t classified by the timestamp
The time stated is the timestamp of the block and not the received time. As you have identified, the block timestamp doesn’t have to be sequential. Hence, it would be perfectly fine for the timestamp of a future block to come before the timestamp of an earlier block so long as it fulfils the Median Past Time.
Pools would usually try to broadcast the block immediately, or with minimal delay and propagation should he under a minute as well.