I’ll pretend that this isn’t pedantry. I can understand why you’d say this, but I think you just haven’t explored the way that git diff works, including the configuration options it takes.
$ git diff 'HEAD^'
diff --git a/file b/file
index efb8e76..ca03496 100644
--- a/file
+++ b/file
@@ -1,3 +1,3 @@
This is context.
-I am studying tonight.
+I am not studying tonight.
This is also context.
$ git diff 'HEAD^' --word-diff
diff --git a/file b/file
index efb8e76..ca03496 100644
--- a/file
+++ b/file
@@ -1,3 +1,3 @@
This is context.
I am {+not+} studying tonight.
This is also context. diff --git 1/old 2/new
index 7164d6e..61a276c 100644
--- 1/old
+++ 2/new
@@ -1 +1 @@
I am {+not+} studying tonight--word-diff does not
Kernel development involves working with patches a lot, so it made sense to default to that, and --word-diff was added later anyway.
I’ll have to create an alias for my use!