Obviously not. However, most people would be flagged by the interviewer for saying "I was a bit bored", and subsequently discarded unless their skillset is hugely in demand. Modesty is only appreciated when decorated with a dose of positivity.

“Why did you leave?”

A better opportunity presented itself.

Or, “Why are you looking?”

Exploring better opportunities more suited to my skills and personality.

It’s fairly easy to not lie and present things in a favorable way.

That's exactly GP's point. You're not expected to tell the truth as it is, instead offering some euphemism is the "right" way to get hired.

Sounds more like a humblebrag to me.

It is. Actually I'd rather not spend at least ten hours a week waiting for administrative bullshit and just work and not have the 35h work week.