How to reproduce:
1. Open the attached project (look for "ugsdata-glo-p01.hq" in Edits)
2. Go to the Project Settings-> Quality-> VSync Count set to "Don’t Sync"
3. Build for iOS and deploy the Xcode project to the iOS device
4. In the Player set the slider to e.g. 4 (might need to increase it more to reproduce)
5. Open the Profiler Window in the Unity Editor and select your running Player (from step 2) to profile it.

Expected: Frames get shown on every VBlank, if possible, the time between frames will be ~16 ms

Actual: Frames that should be shown closely before the first VBlank at 16 ms instead rush past that first VBlank into the second VBlank with 33ms instead, the time between frames will be 33ms, a lot of time will be spent on WaitForTargetFPS

Reproducible with: 2018.3.14f1, 2018.4.3f1, 2019.1.7f1, 2019.2.0b8, 2019.3.13f1, 2020.1.0b9, 2020.2.0a10

Devices tested:
Reproducible with:
iPad 7th gen (iOS 13.2.2)
iPad Air 2 (iOS 11.0.3)
iPad 9.7 6th gen (iOS 12.1)
iPad Pro 12.9 1st gen (iOS 13.4.1)
Not reproducible with:
iPhone 11 (iOS 13.5.1)
iPhone 8+ (iOS 12.0)
iPhone XR (iOS 13.4.1)
N/A, Samsung Galaxy S9 (SM-G960F), Android 8.0.0, CPU: Exynos 9 Series 9810, GPU: Mali-G72
VLNQA00313, Huawei Y6 Ⅱ Compact (HUAWEI LYO-L01), Android 5.1, CPU: MediaTek MT6735, GPU: Mali-T720
VLNQA00316, Samsung Galaxy Note10 (SM-N970F), Android 9, CPU: Exynos 9 Series 9825, GPU: Mali-G76

Notes:
- step 2 might be unnecessary as iOS supposedly just entirely ignores that setting