This is an internally consistent theory, but does not really connect with my own personal anecdotal observations.

I have very poor hearing, and I really a great deal on context, and contextualising speech, to work out what people are saying, and that's the same whether they are native English speakers, Europeans, or Asians. I certainly haven't noticed Asians employing less contextualisation.

What I have noticed is that the recognition of English words relies a lot on stress patterns. Our unstressed vowels turn into schwas or obscure vowels so the stress pattern also affects which vowels get pronounced in their true colours. (One example: a group of European ESL students told me they had dined at "mAk-dun-ahlds" and it took several minutes before I twigged they had been to "mək-DON-əlds". A change of stress can make an English word unrecognisable.

I understand that the Japanese language is unstressed, whereas the European languages tend to be stressed, albeit not as irregularly as English. So ... I don't know, but I'm wondering, if there is a lasting difficulty for Japanese users of English, whether this might be due to the need to acquire the habit of using stress patterns?

I think this use of double words is a necessary reaction to the blurring of literal and figurative uses of words. For example, many businesspersons have a 'mobile office' that consists of their smartphone and laptop. But they may also have a bricks-and-mortar office with a desk, chair, landline, and fellow office workers. How should one differentiate them? We can't really say that the latter is the 'real' office, as the mobile office performs its function in real ways and therefore wins the status of a 'real office'. A quick and unambiguous way is to call the latter the 'office office'.

The other examples given by Judith seem equally valid. Using duplication avoids having to use provocative or insulting expressions:
"happy or happy happy" = "genuinely happy or just faking it"; "fixed or fixed fixed" = "fixed the underlying cause or just kludged it";
"type or type type" = "type professionally or stumble along in an amateurish two-finger effort"

I don't think I'm going to use duplicate words in this way, but I think it's a legitimate addition to the language. It may not be English English but it is English.

As I have just come across this question in a proofreading context, I read the foregoing comments with interest. In British English, the adjectival use of "couple" is unheard of, so "a couple apples" is not just wrong but jarringly so. In US English, I have noticed that "couple" is sometimes a noun and sometimes an adjective. What I gather from these comments (and from other pages) is that the adjectival use of "couple" (as in "a couple apples") is widely use in spoken and colloquial written English in the USA, but the nominal use of "couple" (as in "a couple of apples") is acceptable everywhere and is required in formal writing in the USA.

I disagree with those commentators who see this as a decline in US English. There is nothing illogical in the adjectivalisation of "couple". It is a fate that has befallen other nouns of quantity such as "dozen" and "hundred" without adverse effect. For example, in Richardson's New English Dictionary (1827), we read that "a century is a hundred of years, of men, of anything", a usage that now sounds jarringly wrong. We are none the worse for having made an adjective of "hundred". Although "a couple apples" now sounds illiterate to British ears, I daresay we will grow to accept it too.