There's a little buglet in #85387 (which was the PR that closed #84046), specifically, it doesn't account for the possibility that there's both a default/request **and** and a final pipeline, and that they can both touch the `@timestamp` field.

`IngestService#postIngest` was added in #85387, and it's intended that the logic there only runs **once**, after all the pipelines associated with the request have been executed. But as it's currently written, the logic actually runs after each individual pipeline runs.

The consequence of that is that if there's a default/request and a final pipeline in use for a document, and the final pipeline changes the timestamp field, the `rawTimestamp` recorded for the `IndexRequest` associated with the document will mistakenly use the value it sees after the default/request pipeline runs, and **not** the most correct one (from after when the final pipeline runs).

/cc @martijnvg 
server/src/main/java/org/elasticsearch/ingest/IngestService.java
/**
     * Used by this class and {@link org.elasticsearch.action.ingest.ReservedPipelineAction}
     */
    public static class DeletePipelineClusterStateUpdateTask extends PipelineClusterStateUpdateTask {
        private final DeletePipelineRequest request;
        DeletePipelineClusterStateUpdateTask(ActionListener<AcknowledgedResponse> listener, DeletePipelineRequest request) {
            super(listener);
            this.request = request;
        }
        /**
         * Used by the {@link org.elasticsearch.action.ingest.ReservedPipelineAction}
         */
        public DeletePipelineClusterStateUpdateTask(String id) {
            this(null, new DeletePipelineRequest(id));
        }
        @Override
        public IngestMetadata execute(IngestMetadata currentIngestMetadata, Collection<IndexMetadata> allIndexMetadata) {
            if (currentIngestMetadata == null) {
                return null;
            }
            Map<String, PipelineConfiguration> pipelines = currentIngestMetadata.getPipelines();
            Set<String> toRemove = new HashSet<>();
            for (String pipelineKey : pipelines.keySet()) {
                if (Regex.simpleMatch(request.getId(), pipelineKey)) {
                    toRemove.add(pipelineKey);
                }
            }
            if (toRemove.isEmpty() && Regex.isMatchAllPattern(request.getId()) == false) {
                throw new ResourceNotFoundException("pipeline [{}] is missing", request.getId());
            } else if (toRemove.isEmpty()) {