I think "hugely inefficient" was meant not so much in terms of space requirement or number of strokes, but rather in terms of cognitive load and time required to master it.
While English might be among the worst alphabetic writing systems (compared to, say, Spanish, which has a wonderful correspondence between what is written and what is spoken), it is certainly a more efficient writing system than Chinese, in that fewer years of school have to be dedicated to just learning to read and write.
Furthermore, as highlighted by someone else, it is not uncommon for writers of Chinese to just completely forget how to write a word.
In English, you might misspell it, but it'll be rare that you can't render it at all.
Not necessarily true.
For instance, "Not necessarily true" is 18 characters and 2 white spaces, while in Chinese, it could be as simple as "未必".