How to reproduce:
1. Create and open a new Unity project
2. Set up perforce version control on it and close the project
3. Open "manifes.json" from the Packages folder
4. Change "com.unity.timeline" version to 1.2.14 and save the file
5. Open P4V client and login with the same Workspace as the one used in step 2
6. In P4V navigate to the Packages folder containing "manifest.json" and "packages-lock.json" files
7. Submit "manifest.json" and "packages-lock.json" files
8. Open the project with a newer version of Unity
9. Click "Yes" when asked, "Would you like to make these files writable?"

Expected results: when making files writable Package Manager also checks them out in the chosen Version Control system
Actual results: files are made writable without checking them out

Reproducible with: 2019.4.5f1, 2020.1.1f1, 2020.2.0a19
Could not test with: 2018.4.25f1 (packages-lock.json doesn't exist)

Notes:
-The issue also reproduces with Plastic SCM Version Control system