The absolute best in any field including fast food cook is probably as intelegent as any other field. However the average really can be meaningfully different based on self selection. HR for example really does not attract the best and brightest.
Sales is an outlier because compensation for the best can be really good. So, it's got a large group of very talented people and many far less so.
There's always the difficulty of being able to recognise that as a lamen. Mediocre sales people are often transparent to anybody who listens to them and is able to ask questions. A mediocre engineer "blinds with science" and is very hard to identify without some amount of specialist knowledge.
'proper' Engineering (MECH/AERO/CIVIL/EEE) is full of memes about this mindset.
CS is just as bad.
Most decent engineers loose this mindset after freshman year but many go on to see them selves as the MVP department of whatever business.
In some ways I think Startup culture fights against this because it's really obvious at small team scale how different skill sets are needed.