The address data in Parish Online is updated on a nightly basis from every Local Authority in the country, via the national addressing hub (GeoPlace). This database includes addresses for properties that are currently being built.
Because the Local Authority will not have the perfect position for those addresses (because they've not been built yet, so Ordnance Survey can't survey them), then they place them in generally the correct position, usually based on a plan from the developer.
As the properties are built and aerial photography and Ordnance Survey mapping becomes available for them, the Local Authority will adjust their position to sit within the building outline.
So, don't worry if you see them floating around in odd places; they will improve. The timing for these improvements vary by Local Authority area.
It's useful to include this information as it means Local Councils can get address information for new addresses. But bear in mind that the address, postcode or position may change through it's build phase.
You can switch on the
Recent Changes layer to highlight address points which have had changes made.
Here's an example of addresses for properties being built.