Thanks for bringing this up @Victuallers. This is normally something I would have discussed before going ahead with but it's been rushed along a bit to try and have them ready before Wiki Loves Monuments finishes!
I was planning on doing the import as you expected it should be, but realised it makes it impossible to use the coordinate locations in the data provided by Historic Environment Scotland - their data is divided into individual buildings, with an "ENTRY_SEQ" field to record which building it is in the series (they will all share the same main ID) . For some IDs there is only one building, but others are made up of groups of buildings that aren't necessarily next to each other.
So what I've done for now is import each row from the source data, but have given the Historic Scotland ID (P709) statement a series ordinal (P1545) qualifier to say which building it is in the series. The series ordinal qualifier matches the value for the ENTRY_SEQ field in the source data. This makes it easy to merge items together on mass if we need to, or update in the future if we end up keeping this granularity.
I have to say I do prefer reducing this to the single item for each "listing". I still feel we may end up needing different items for each building, but using 'part of' or something to link them to the main item for the listing. I'm sure many will see this as overkill though! The main issue to solve is how to have the coordinates of the individual parts well described. Any ideas?