You shouldn't editorialize, but you are allowed to change titles.
The author specifically says he is talking about hard for english speakers, so the new title is correct.
Specifically:
"Languages tend to get “harder” the farther one moves from English and its relatives. Assessing how languages are tricky for English-speakers gives a guide to how the world’s languages differ overall."
and
"A truly boggling language is one that requires English speakers to think about things they otherwise ignore entirely."
The author specifically says he is talking about hard for english speakers, so the new title is correct.
Specifically:
"Languages tend to get “harder” the farther one moves from English and its relatives. Assessing how languages are tricky for English-speakers gives a guide to how the world’s languages differ overall."
and
"A truly boggling language is one that requires English speakers to think about things they otherwise ignore entirely."
as two examples.