I'd agree with Rolf that it's not helpful to have this attribution at activity level when organisations will be reporting on a range of different types of indicators. However, I also think that it's important to have some kind of flag on the data to show that the data under the indicators should not be aggregated, especially where indicators have been developed for a specific project/context and it would not be appropriate to aggregate the data with that from another context.
Data users will naturally want to aggregate, and a flag is not going to stop them from doing so. However, it's a way for the reporting agency to flag to users that it should not be aggregated, in order to protect the integrity and trust in the source data.
I think the results element is very much still in development and as more organisations start using it, it will be improved and there may be less of a need for this flag. However where we are at present, I feel it should be preserved at indicator level.
I think Rolf has also raised an important question around dimensions, and I'd be interested to hear from others about a potential solution?