onDrop's arguments dropPosition not equal allowDrop's arguments dropPosition

import RcTree from "rc-tree";
import "rc-tree/assets/index.css";

const treeData = [
  {
    title: "title0",
    key: "key0"
  },
  {
    title: "title1",
    key: "key1"
  },
  {
    title: "title2",
    key: "key2"
  },
  {
    title: "title3",
    key: "key3"
  },
  {
    title: "title4",
    key: "key4"
  },
  {
    title: "title5",
    key: "key5",
    children: [
      {
        title: "title4-0",
        key: "key4-0"
      },
      {
        title: "title4-1",
        key: "key4-1"
      },
      {
        title: "title4-2",
        key: "key4-2"
      },
      {
        title: "title4-3",
        key: "key4-3"
      }
    ]
  },
  {
    title: "title6",
    key: "key6"
  }
];

export default function App() {
  return (
    <RcTree
      allowDrop={(params) => {
        if (Math.random() > 0.99) {
          console.log("allow drop:", params);
        }
        return true;
      }}
      onDrop={(params) => {
        console.log("on Drop:", params);
      }}
      draggable
      defaultExpandAll
      treeData={treeData}
    />
  );
}

quick codesandbox

try to drag title4-3 as first child(before title4-0), and see console

Start with the linked CodeSandbox reproduction and compare the parameters logged by allowDrop and onDrop while dragging title4-3 before title4-0. Trace the drag-and-drop entry point used by RcTree, then verify that both callbacks report the same dropPosition for this case.