I’m assuming you are American and therefore don’t converse with other Americans much while abroad. If you’re in Europe, the weather forecast is in Celsius, you would be seeing 22 everywhere but your phone. When conversing with someone, unless you’re a complete arrogant ass (well these are Americans and you admitted to doing the same and now everything makes sense….) you would use the local units. So you would use Celsius, than slip up when following g up about your local place.

Again, this is already an issue an happening, you just don’t notice it from your side point of view. Hell most won’t even realize they made the folly.

And it’s not different, you said you could tell by context, I provided you a very real situation that already happens that would not allow you to tell the unit by context. And now you’re arguing completely different points.

The inverse even happens in the states when getting visotors, most visitors use the local units and slip up when talking about home, but they usually denote units already since they know it’s an issue when conversing with Americans. It’s a real thing if you don’t choose to ignore it because murica.