i had a discussion with some of my co workers about escaping strategies and when to use 'html_attr'.

from my point of view, we should add an example when to use html_attr instead of html.

The docs are saying that:

html: escapes a string for the HTML body context.
html_attr: escapes a string for the HTML attribute context.

example 1

following the docs, this wouldn't be best practice, but it seems to be "fine".
#2615 (comment)

{% set untrusted = 'untrusted' %}
<div class="{{ untrusted }}">{{ untrusted }}</a>

example 2

if you stick to the docs this should be best practice?

{% set untrusted = 'untrusted' %}
<div class="{{ untrusted | e('html_attr') }}">{{ untrusted }}</a>

is there any reason why example1 is wrong?