I could see that perhaps the uploader submitted this when there wasn't already chapter 5 from Senko-San's posted (I saw another series in teh last few days that had an apparent snipe but a site admin popped in to say that the supposed duplicate chapter had been stuck in the approval queue for weeks for unspecified reasons, meaning it significantly pre-dated the other chapter that popped up before it)
but that doesn't really explain why someone would jump on a series that is being attended to regularly by another group and has had multiple chapters posted in the last few weeks.
There are dozens of series out there that have been left to rot by vanished/disbanded groups or drops. Any of those would make far better practice targets because it would probably get more slack from the audience that's just happy to have anything posted for that series. In that case everyone wins. Doubling up on something that's being done and done well on a current schedule only invites scorn.