Bug: Query-frontend 2.14 doesn't return complete timeseries in case of multi-tenancy

[denraf]

What is the bug?

When using mimir 2.14, the query frontend doesn't return the full timeseries when the tenants have different retention settings.
When just switching the query-frontend back to 2.13 all data shows up as expected with a multi-tenant datasource in Grafana.

How to reproduce it?

Grafana datasource, with header X-Scope-OrgID: main|linkerd

Helm-distributed 5.5.0 install with config:

mimir:
  structuredConfig:
    # https://grafana.com/docs/mimir/latest/references/configuration-parameters/#limits
    tenant_federation:
      enabled: true
    limits:
      max_global_series_per_user: 100000000
      ingestion_rate: 2000000
      ingestion_burst_size: 50000000
      max_label_names_per_series: 50
      compactor_blocks_retention_period: 1y
    ruler:
      tenant_federation:
        enabled: true
runtimeConfig:
  overrides:
    linkerd:
      compactor_blocks_retention_period: 30d

What did you think would happen?

Metrics belonging to the main tenant are visible for the full year.

What was your environment?

Mimir 2.14
Kubernetes 1.30

Any additional context to share?

When creating a new datasource in Grafana with X-Scope-OrgID set to main only, metrics for the full year are visible.

[denraf]

Related to #9727