How do I get a terms aggregation to respect the pipeline above it? - elasticsearch

Question

(I've attached test data below the question)
I would like to know why when I use min_doc_count of a terms aggregation that is inside a pipeline aggregation, does it not respect the results of the aggregation above it?
Here's my query:
{
"size": 0,
"query": {
"bool": {
"filter": [
{
"nested": {
"path": "facets",
"query": {
"bool": {
"filter": [
{
"term": {
"facets.name": "brand"
}
},
{
"term": {
"facets.value": "hokey"
}
}
]
}
}
}
}
]
}
},
"aggs": {
"facets": {
"nested": {
"path": "facets"
},
"aggs": {
"names": {
"terms": {
"field": "facets.name"
},
"aggs": {
"values": {
"terms": {
"field": "facets.value",
"min_doc_count": 0
}
}
}
}
}
}
}
}
Looking at the above, and with using min_doc_count=0 for the facets.value term, why am I seeing results for all possible facets.value even when they don't match the above facets.name?
Surely, the aggs should be hierarchical and respect the higher levels? Do I need to run a script filter or something?
Please experiment with the below data to see what I mean. I don't want to have to run multiple queries for our search filtering because without min_doc_count because lots of facet.values are filtered out, but with it, we have too many irrelevant results in the lowest aggregation.
Mapping:
{
"mappings": {
"properties": {
"facets": {
"type": "nested",
"properties": {
"name": { "type": "keyword"},
"value": { "type": "keyword"}
}
}
}
}
}
Bulk documents:
{ "index": { "_index": "product-facets", "_id": 1} }
{"facets":[{"name":"brand","value":"ubest"},{"name":"color","value":"green"},{"name":"department","value":"soccer"}]}
{ "index": { "_index": "product-facets", "_id": 2} }
{"facets":[{"name":"brand","value":"ubest"},{"name":"color","value":"green"},{"name":"department","value":"adventure"}]}
{ "index": { "_index": "product-facets", "_id": 3} }
{"facets":[{"name":"brand","value":"beert"},{"name":"color","value":"white"},{"name":"department","value":"soccer"}]}
{ "index": { "_index": "product-facets", "_id": 4} }
{"facets":[{"name":"brand","value":"ubest"},{"name":"color","value":"yellow"},{"name":"department","value":"adventure"}]}
{ "index": { "_index": "product-facets", "_id": 5} }
{"facets":[{"name":"brand","value":"hokey"},{"name":"color","value":"yellow"},{"name":"department","value":"adventure"}]}
{ "index": { "_index": "product-facets", "_id": 6} }
{"facets":[{"name":"brand","value":"beert"},{"name":"color","value":"black"},{"name":"department","value":"casual"}]}
{ "index": { "_index": "product-facets", "_id": 7} }
{"facets":[{"name":"brand","value":"hokey"},{"name":"color","value":"white"},{"name":"department","value":"adventure"}]}
{ "index": { "_index": "product-facets", "_id": 8} }
{"facets":[{"name":"brand","value":"ubest"},{"name":"color","value":"black"},{"name":"department","value":"casual"}]}
{ "index": { "_index": "product-facets", "_id": 9} }
{"facets":[{"name":"brand","value":"hokey"},{"name":"color","value":"white"},{"name":"department","value":"soccer"}]}
{ "index": { "_index": "product-facets", "_id": 10} }
{"facets":[{"name":"brand","value":"hokey"},{"name":"color","value":"white"},{"name":"department","value":"adventure"}]}