Strong disagree, I did sales (I would like to think successfully) for a long time as someone who struggled with depression and anxiety, there's far more to it than just having a fake smile plastered on; people like those who can empathize with them, understand their needs, etc. and sometimes a no-bs straightforward approach talking pros and cons directly instead of a fake used-car salesmanesque over the top approach is far more effective.
I did non-commission sales for a while as well, and made no effort to appear more happy than I was. People appreciated my candor and knowledge, rather than being won over by my charm. I sold a lot of stuff, and there was even a time that a customer found out I wasn't in that day and decided to come back another day instead of dealing with anyone else, even knowing there were no commissions.
My proof that I did well at it was that management constantly told me I need to upsell more and tried to scare me into it, but at no point did they ever actually move to take me off the sales floor. They knew I did really well, even without their extra BS items to push.
The most successful salesperson I know has a pretty flat affect but knows her product super well and is excellent at needs analysis. There’s definitely a lot more to sales than glad handing people with a smile.
I was a successful retail and enterprise salesperson earlier in my career. I also suffer from lifelong depression.
I did not fake "happy happy joy joy," but I also did not allow self absorption to inject my mood into my business. My model is that sales is a career that involves having structured communications.
That was a lifesaver for me when feeling depressed, because I could focus on the structure of what needed to be accomplished rather than the unstructured touchy-feely business of "getting along with people."
I suggest that "YMMV." Salespeople are not all the same, and some break preconceptions and stereotypes hard while being successful at what they do.