Reproduction steps:
1. Download and open the user-submitted project "TestProjectUIToolkit.zip"
2. Open the VisualElementsArray scene
3. Open build settings (File -> Build Settings)
4. Add the open scene to the build
5. Build and run for Android
6. Set the Console to log the Android player
7. Press on the bottom of the green rectangle in the build

Expected result: touch down, mouse down, touch up and mouse up is logged for the GreenElement
Actual result: touch down, mouse down, touch up and mouse up is logged for the GreenElement and BlueElement

Reproducible with: 2020.1.17f1 (UI toolkit 1.0.0-preview.13)
Could not test with: 2018.4, 2019.4 (UI toolkit is not available)
Could not test with: 2020.2, 2021.1, 2021.2 (Issue 1269167 makes UI Toolkit unusable)

Reproduced on:
Device Simulator
VLNQA00012, Samsung Galaxy S6 (SM-G920F), Android 7.0, CPU: Exynos 7 Octa 7420, GPU: Mali-T760
----------, Samsung Galaxy S9 (SM-G960F), Android 10, CPU: NOT FOUND, GPU: Mali-G72
VLNQA00321, Xiaomi MI 9 (MI 9), Android 10, CPU: Snapdragon 855 SM8150, GPU: Adreno (TM) 640
iPhone 12 Pro (iOS 14.2.1)

Does not reproduce on:
Windows Editor
Windows Standalone

Workaround: Changing the "Screen Match Mode Parameters) match value to 0.5 in the Panel Settings would prevent the issue.