I hear you on this, I spent my late teens through my 20s and 30s living abroad and learning other languages. I’ve since moved back home and had kids. I had to break out my Spanish a few times in the past year or so and both my kids did a double take/didn’t know what the hell was happening when they saw me speaking passable/semi-fluent Spanish to native speakers.
I’m just your average stay at home Dad living in a small town nowadays but had a wildly international life before settling down. When they saw me speak another language the questions started to come out about where I had been or what I had been doing.
I hadn’t spoken about it much to my kids when they were younger but now, based on their questions, I half suspect that they think I was some sort of international spy. Nope, just a lot of wanderlust, a knack for languages and learning about the psychology of other cultures first hand.
There are so many tells with lies that they can be easy to spot once you know enough of them. Not all tells are absolute across everyone but if you know enough of the tells you can see them easily when several present themselves all at the same time.