Why am I being offered four communities - don't you know?

Because the surname really is shared. Several communities carry your surname in your district, and no honest system can tell them apart from the name alone — so Saath suggests instead of deciding.

The list is ordered with your best matches first. Where the match comes from your whole state rather than your district specifically, it says so next to the option, with the confidence shown plainly. Your district is what narrows it: some labels stay genuinely ambiguous until the district is known, which is why you are asked for it. And if none looks right, "not sure" is the honest answer.