Yeah, if I was a non-native English speaker, I'd be nonplussed about the word (both meanings).
But some commonly used words are confusing. Sanction means both to allow and to disallow. Literally is a nightmare, especially in written form, but also spoken without enough cultural context.
I don't like all these examples, but here's a list of 40 mostly common words or two word phrases that mean their opposite. [1] There's probably 10-20 of those that a new to English speaker is likely to run into. But then, I never got far enough into other languages, maybe this is a common phenomenon.
> But some commonly used words are confusing. Sanction means both to allow and to disallow.
Well, technically, it means to allow or to punish. But you're close enough. It does have these two senses, they are obviously in tension with each other, and both are common.
But, because both senses are common, this isn't a source of confusion. (And the later sense of punishment did not arise from confusion on the part of speakers, as is the case for nonplussed.)
Which means it's of particularly limited use to a foreign speaker.