The ambiguity of which length is being talked about is what smells. It is a bad odor, not bad enough that I'd not use a library that had 'length' as a property, but it is absolutely a smell because I can't be sure that every single last usage of 'length', inside the library nor in my code, is using the same definition for 'length' as is meant.

It's subtle, which is what makes it a smell, rather than a "DO NOT WANT".