The example is taken from page 1 of this PDF ; The National Admissions Test for Law (LNAT):
You may find, however, that answering one question helps you answer the next, not least for the purposes of elimination as well as general understanding of the subject matter and the structure of the main and subsidiary arguments.
User AmeliaBR's answer states:
The phrase you quote for not least can't be replaced directly with notably, because it is not really comparing equivalent parts of speech of which one is not least: not least is followed by a phrase that starts with "for" ("for the purposes of") but the alternative ("general understanding") isn't introduced with "for". To be clear: The phrase is grammatically poor even with not least, switching to notably only emphasizes the problem, it doesn't create it.
What are the problems here? Can 'for' follow notably? Why or why not? Google Books produces many results for 'notably for', so this appears justified?