Stream event type num_variants_in_stream no longer observed

{
  "har.sse_event_types": [
    "__debug",
    "conversation_detail_metadata",
    "event:delta",
    "event:delta_encoding",
    "hidden",
    "input_message",
    "message",
    "message_marker",
    "message_stream_complete",
    "product_entity",
    "product_rationale",
    "product_reviews",
    "resume_conversation_token",
    "search_model_queries",
    "search_result",
    "search_result_group",
    "server_ste_metadata",
    "sources_footnote",
    "stop",
    "title_generation",
    "url_moderation"
  ]
}