PS, source for it being added is stated as os_opendata_streetview.

commercial edition of OS map hosted at streetmap.co.uk does not mark this as a POW. That map does mark Lerwick Congregational Church as a POW on the south side of the road. Both of those observations are at odds with  "OS OpenData StreetView (April 2016)" as it appears on the iD background layer

could this be an Easter egg?