Why does only part of git console output go into log file?

On Windows, I have a bat file that creates a git commit like so:

@echo off
echo.
echo -------------------------

cd C:\Repository\Other\notes-repo
git add --all
git commit -m "autoCommit"
git push
cd C:\Repository\Other

I call it from the command line like this:

note_repo_sync.bat >> log.txt 2>&1

When there are changes to the repo, then this gets added to the log file:

-------------------------

[main 013c443] autoCommit
 1 file changed, 1 deletion(-)
To https://github.com/raelb/notes-repo.git
   6bceead..013c443  main -> main

However, if I omit the 2>&1, i.e. print the stderr to console, then much more is shown:

C:\Repository\Other>notes_repo_sync.bat >> log.txt
Enumerating objects: 5, done.
Counting objects: 100% (5/5), done.
Delta compression using up to 4 threads
Compressing objects: 100% (2/2), done.
Writing objects: 100% (3/3), 290 bytes | 290.00 KiB/s, done.
Total 3 (delta 0), reused 0 (delta 0)
To https://github.com/raelb/notes-repo.git
   28a2bf3..691fb4f  main -> main

Why are the extra lines (Enumerating objects etc..) not included in the log when I append 2>&1 to the command line?

>Solution :

Both git fetch and git push write their progress information (--progress output, suppressed with --no-progress) to standard error. Progress output is suppressed by default when stderr is not connected to a terminal.¹

There’s no particularly good reason for this, other than "Git used to do this for historical reasons, so Git still does this for historical reasons".

¹There are, or were, further bugs where explicit --progress didn’t always work to restore the stderr output even when stderr is connected to something other than a terminal.