When people don't have any actual evidence to support their claims, they use bullshit phrases designed to push emotion over facts.
Often I'll use emotions over facts even when I have facts. My own experience has been that discussing with other humans goes easier when you include emotional arguments. While a mix of both works best, if you have to give a very simplified argument and cannot include both factual and emotional argument, the emotional argument will tend to go better.
I fully agree with your claim that those without factual argument will use emotional argument, but the use of an emotional argument does not guarantee they are lacking a factual argument.
For example, if I describe someone as an intern due to their lack of maturity, I may have numerous stories to tell about their lack of maturity, but as I only have one line to describe them in, I stick with describing them as an intern.
Besides "he looked just out of high school" can be corroborative evidence, as it's something that can statistically explain their immature behavior/inexperience etc.
In other words, it's not like everybody who is "just out of high school" is immature/inexperienced etc, but if we want to predict or explain such behavior, it's a statistically very good tool.
It can also mean that he looked AND acted inexperienced, immature, bro-ish, etc.