Some of the biggest surprises and worst hires I've seen is people who are extremely slick in interviews. My mother has similar stories from working for a major financial institution for 35 years. She had consistently told me growing up over the years that half the time the best educated folks were all super slick in interviews and stellar on paper and then lazy as hell on the job.
The actually-good end up having to do precisely the covering-up you mention, because genuine and entirely fine attitudes and behaviors are, in interviewers' imaginations, often magnified to their worst possible extremes. It's very valuable information for a good employee to have that they need to cover up or avoid certain things in interviews that aren't actually a problem, because they do need to do that, and they may not realize how things that they think aren't a big deal and in fact are not are coming across in an interview context.
I write this as someone who is, I gather from feedback, pretty decent at that part of interviewing. Doesn't make it less gross-feeling and stressful.