Reproduction steps:
1. Create a new "3D (Built-In Render Pipeline)" project on 2020.3.48f1 with Unity Hub
2. Open the created project
3. Enter the Play Mode
4. In the Play Mode overlay, press the "Stats" button
5. Observe the FPS (on the machine this was tested on, average FPS was around 700-800)
6. Exit the project
7. Open the same project with a newer version
8. Enter the Play Mode
9. Observe the FPS in the "Stats" window

Expected result: Average FPS stays about the same as in 2020.3.48f1
Actual result: Average FPS goes down to around 500-600 (depends on the machine)

Reproducible with (when upgraded to): 2023.1.0a20, 6000.0.30f1, 6000.1.0a7
Not reproducible with (when upgraded to): 2021.3.46f1, 2022.3.53f1, 2023.1.0a19

Reproducible on: Windows 10 (22H2)
Not reproducible on: No other environments tested

Notes:

* The results can easily be inconsistent depending on the other processes running on the computer, so it’s best to test this on a freshly restarted computer with no other applications running in the background
* Player, with VSync disabled, shows around 3000 FPS (used a custom script to display the “Stats“ information on the screen), so will leave this as the Editor issue
* Tested on Alienware M15 R4, 32 GB RAM, i9-10980HK @ 2.40GHz, NVIDIA GeForce RTX 3080