Well, yup, ideally...we should all tell the truth all the time

But, in reality, it is more complicated than that... and sometimes, the truth really isn't important.
This is very much so with our community. A lot of us go through extremely sensitive times with respect to how we look... and, even though we don't "pass", a lie now and then can at least help us feel better for a little bit as we keep transitioning and get through things.
Always giving people straight honest answers is a very bad idea. They are already very aware of their flaws and probably beat themselves up constantly over them... so... saying they look pretty or they are doing great or other types of support isn't doing any real harm.
Now, of course, maybe avoid telling them they pass (just so they won't try going full time too soon...which is a huge problem people do)... but, everything besides that is great to say.
If you read those threads, you have those who lie about how people look... and then you have the "honest" ones who start emotionlessly listing all the things wrong with someones face... and it really seems like the "honest" ones are the ones that cause more harm ....