I ran into this exact issue before 
Bubble’s CSV export workflow is kinda annoying with related fields. Instead of exporting the actual values, it just spits out the unique IDs for linked objects.
From what I found, changing the “primary field” only really works in some cases (like User email), but not consistently for other related data types.
Honestly, the easiest workaround is usually building the export from a repeating group or using a CSV plugin instead of the default workflow export. The built-in export feels super limited once relationships are involved.