RUN_OS_WINBASH_IS_LINUX does not work in VS Code git bash terminal

[pot2mayo]

The possibility to set the RUN_OS_WINBASH_IS_LINUX environment variable to make git bash being seen as a Linux terminal is great, and it works well if git bash is started on its own.

However if you start git bash within Visual Studio Code, the check condition does not work anymore and the terminal is always seen as Windows.

Here is what I get in a git bash terminal spawn independently.

> process.env.SHELL
'C:\\Program Files\\Git\\usr\\bin\\bash.exe'
> process.env.TERM_PROGRAM
'mintty'

Hence the condition works.

However same commands in git bash spawned within VS Code and I get

> process.env.SHELL
undefined
> process.env.TERM
'xterm-256color'
> process.env.TERM_PROGRAM
'vscode'

EDIT:
It turns out the terminal does not behave the same way if you start a new first instance within VS Code (instance on the left in the capture below) or if you split a second terminal from the first one afterwards (instance on the right)