`tagged_subqueries` move-in latency is ~15 seconds while regular replication is instant

When using `tagged_subqueries` with a shape like:

```sql
WHERE id IN (SELECT user_id FROM workspace_members WHERE workspace_id = $1)
```

I'm seeing ~15 second latency for move-in events, while regular replication events are instant.

**Observed behavior:**

1. Insert a new `workspace_members` row → syncs to client in <1 second
2. The corresponding `profiles` move-in takes ~15 seconds to arrive
3. During this gap, the UI shows the new member but can't display their profile data

**Expected behavior:**

Move-in events should arrive with similar latency to regular replication events.

**Environment:**
- Electric server: `electricsql/electric:latest` on Railway
- Client: `@electric-sql/pglite-sync` 0.4.1

**Questions:**
- Is this expected behavior for the Materializer?
- Is there any configuration to reduce move-in latency?
- Is this something being optimized?