Hitting 'C-u C-x =' on the first 7 and the backslashes says:

  There are text properties here:
    face                 (font-lock-variable-name-face font-lock-string-face)
    fontified            t

On the next two forms, I get:

  There are text properties here:
    face                 font-lock-string-face
    fontified            t

Is this difference on purpose?

Best, Arash

In GNU Emacs 30.0.50 (build 1, aarch64-apple-darwin23.2.0, NS
 appkit-2487.30 Version 14.2.1 (Build 23C71)) of 2024-01-07 built on
 MacMutant.fritz.box
Repository revision: f866c85ac4e32df8061b285b6b44b15346994f3d
Repository branch: master
Windowing system distributor 'Apple', version 10.3.2487
System Description:  macOS 14.2.1

Configured using:
 'configure --with-ns --without-pop --without-mailutils --with-threads
 --with-modules --with-native-compilation --without-compress-install
 'CFLAGS=-O2 -g0 -pipe'
 'CPPFLAGS=-I/opt/homebrew/Cellar/gcc/13.2.0/include
 -I/opt/homebrew/Cellar/libgccjit/13.2.0/include
 -I/opt/homebrew/Cellar/gmp/6.3.0/include'
 'LDFLAGS=-L/opt/homebrew/Cellar/gcc/13.2.0/lib/gcc/current
 -L/opt/homebrew/Cellar/gmp/6.3.0/lib''

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Important settings:
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix