Related issue for D6 and D7 here:
#1211264: Set the view title to term name when filter argument is term id
In D8, the issue seems to continue. I am actually trying to override term pages for Products (Commerce). So, the Product entity doesnt have the usual "Has Taxonomy Term" filter. Instead I am using term field. When I try to override title, i am using twig as:
{{ arguments.field_kategori_target_id }}
I also do validation with Term ID and select "One or more IDs separated by , or +"
The title shows term ID instead of term NAME.