Note the warning at the beginning of the article: it needs attention; in particular it needs useful references. The first sentence has a footnote that refers to 'Collins and Mees', but this is not listed in the bibliography. I presume it refers to Practical Phonetics and Phonology: A Resource Book for Students Routledge English Language Introductions: Amazon.co.uk: Beverley S. Collins, Inger M. Mees: Books.
I can almost hear the author's Linguistics 101 lecture saying 'Get out your Collins and Mees'. And the note in Wikipedia only says that its examples (not its statements) are from that book. Generally I think the way the article expresses itself is questionable. Assimilation of the kind described does sometimes occur. But if you go out of your way to say things like /lʊk ɪn nə bɒks/ you will only raise eyebrows.