Reproduction steps:
1. Open the project in Repro.zip and open SampleScene
2. Build WebGL and host on http server (python3 -m http.server <port>)
3. Open the hosted URL on iOS device
4. Drag your finger along the right side of the screen (grey transparent area)

Expected result: On Drag event is called instantly (will be debugged on right side of the screen)
Actual result: On Drag is not being delayed until first message appears (after that it seems to work fine)

Reproducible with: 2019.4.29f1, 2020.3.13f1, 2021.1.14f1, 2021.2.0a1, 2021.2.0b3, 2022.1.0a1
Could not test with 2018.4.36f1 (precompiled assembly exceptions)

Reproduced on Chrome and Safari

Devices tested:
iPad Pro 12.9 (iOS 13.4.1) (delay is around 5 seconds)
iPhone 12 (iOS 14.1) (delay is around 1 second)
OnePlus A5000, Android 10, Adreno 540, Snapdragon 835 (delay is around 0.5 seconds)

Note: After some time of first drag the callouts appear in debugger with a delay, after that the messages are debugged properly (the value which is -1 in editor is close to max int on iOS though, not sure if this is relevant)