Reproduction steps:
1. Download and open the submitted project "RefreshRateTestProject.zip"
2. Build and run on Android
3. Note the logged values
4. Open settings on your device and leave the build running in the background
5. Change the device's screen refresh rate
6. Return to the build

Expected result: The printed values match
Actual result: The printed values don't match

Reproducible with: 2018.4.28f1, 2020.1.0b1, 2020.2.0a2
Does not reproduce with: 2019.4.0f1, 2020.1.0b2, 2020.2.0a3, 2021.1.0a1

Reproduces on:
VLNQA00335, Samsung Galaxy S20+ 5G (SM-G986B), Android 10, CPU: Exynos 990, GPU: Mali-G77
OnePlus 7 Pro (reported by the customer)
Google Pixel 4 (reported by the customer)

Could not test on (refresh rate is locked at 60Hz and cannot be changed):
VLNQA00122, Samsung Galaxy S9 (SM-G960F), Android 9, CPU: Exynos 9 Series 9810, GPU: Mali-G72
VLNQA00125, Google Pixel 2 (Pixel 2), Android 8.1.0, CPU: Snapdragon 835 MSM8998, GPU: Adreno (TM) 540
VLNQA00321, Xiaomi MI 9 (MI 9), Android 9, CPU: Snapdragon 855 SM8150, GPU: Adreno (TM) 640

Notes:
The issue is not reproducible on the latest versions of all Unity streams apart from 2018.4.