Typical passive-aggressive behavior, and yes, it stems from a sense of superiority and insecurity.
30 minutes late who wants 45...
Nah, it ain’t that complicated. I had an Aunt that pulled that krap. It’s just arrogant, ill-mannered, incondiderate bad manners with failure to extend common courtesy. Mostly it comes from never having had ones asskicked up between ones shoulder blades at the earliest signs of willfull ignorance.