On using Shift/Cmd(⌘)+ Up arrow(↑) shortcut keys to multi-select Gameobjects from hierarchy window resulting Gameobjects multi-selected inconsistently. refer attached video.

Workaround: Multiselect Gameobjects in Top to the Bottom manner.

Steps to repro:
1. Open the attached project and load multiselect scene.
2. Go to Cube 6 and press Cmd(⌘)+ Up arrow(↑) shortcut key.
3. Hold Cmd(⌘) and press Up arrow(↑) rapidly to multi-select
4. Observe inconsistent multiselection of game objects

Expected result:
Gameobjects should multi-selected consistently.

Actual result:
Gameobjects were multi-selected inconsistently by using Shift/Cmd(⌘)+ Up arrow(↑) shortcut keys.

Occurring on:
2021.1.0a1

Working fine on:
2020.2.0b7, 2020.1.7f1, 2019.4.11f1

Environment:
Occurring on Windows 10 & Mac 10.15.