UnityWebRequest performance drop when running multiple requests at once

Unity: UnityTLS

2023.3.X

2023.2.X

2023.2.0a21 onwards

2022.3.X

2022.3.6f1 onwards

2021.3.X

2021.3.29f1 onwards

2023.1.X

2023.1.4f1 onwards

Fixed in: 2023.3.0a15

Fixed in: 2023.2.0f1

Closing this port as 2023.1 has reached the end of life with 2023.1.20f1

Fixed in: 2022.3.14f1

Fixed in: 2021.3.33f1

How to reproduce:
1. Open the user’s attached “MinRepro.zip” project
2. Enter Play Mode
3. Observe the Console window

Expected result: No errors
Actual result: “UnityWebRequestException: Cannot resolve destination host” errors appear

Reproducible with: 2021.3.29f1, 2021.3.30f1, 2022.3.10f1, 2023.1.14f1, 2023.2.0b10, 2023.3.0a6
Not reproducible with: 2021.3.28f1

Reproduced on: macOS 13.5.2 (Intel)
Not reproducible on: No other environment tested