Summary:
When v-sync is disabled, the frame rate is capped at double the screen's refresh rate. My screen's refresh rate is 144hz, so the frame rate is capped at 288. If I change the refresh rate to 60hz, the frame rate will be capped at 120.

Steps to Reproduce:

1. Navigate to %userprofile%\AppData\Local\Packages\Microsoft.MinecraftUWP_8wekyb3d8bbwe\LocalState\games\com.mojang\minecraftpe
2. Open options.txt and set gfx_vsync to 0
3. Launch Minecraft and observe the frame rate

Observed Results:
The frame rate is capped at double the screen's refresh rate.

Expected Results:
The frame rate should be uncapped.

System Specs:
OS: Windows 11 Home
CPU: Intel Core i5-11400H
GPU 0: Intel UHD Graphics
GPU 1: NVIDIA GeForce RTX 3060 Laptop GPU
RAM: 16GB

This issue occurs with both GPUs and doesn't occur in Java Edition or other games. This issue also doesn't appear to occur on all systems because it doesn't occur on my old laptop.