There are clearly certain activity codes for which who records are not collected, but I cannot find in the FAQ or BLS documentation any mention of the activity universe for which who records are collected.
There is a discussion in the description of RELATEW that this information was collected for work activities beginning in 2010. Is there a list of the other activities for which this is not collected? Additionally, do the same restrictions apply to AGEW and SEXW? (These appear to have the additional universe restriction limiting to only ATUS household members.)