There are many instances of this being false.
Yes, there are a few phonetic inconsistencies in Hindi, but the point remains for most part - Hindi is (largely) a phonetically consistent language.
South Indian speakers of Hindi changed तैयार to तईयार a long time ago, and there hasn’t been any proposals to update it.
(I’ve been saying तईयार since my childhood, picked up from the North Indians around me, so I doubt it’s the South Indians alone.)
नारायणा is actually नारायना in both Hindi and English.
Note that a number of modern mispronunciations and misspellings stem from the prevalance of English, which does not have a number of sounds (in this case, ṇ/ण), and people pronouncing words in English as-is without realizing that they are standing in for a Hindi word with a different pronunciation. I suspect नारायणा/नारायना is one of them.
It’s a bit like Google Maps putting in a fictitious street/place/junction name → everyone starts using that name → someone puts up a sign with that name 
Similar things are true for यह, पर, and वह.
I don’t understand how पर is an example. As for यह and वह (I assume you’re talking about people writing यह/वह but saying ये/वो instead), I think that’s the one real example in your post of people simplifying pronunciation in daily use…also, I think that one’s (way) older than me 
considering that you still write मंडवली as मण्डावली even though I have already told you that the former is a part of official Standard Hindi and also used in common writing by public.
And I already told you
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“Mandawali” is one of the few words in Hindi whose spelling is ambiguous to me, i.e. I don’t know which variant to use.
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In such cases, I defer to using the spelling as written on signage.
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Therefore, I got “मण्डावली” from a signboard.
Also, I personally prefer writing the half-consonant instead of the bindu for sake of clarity. Since (per your own statement) both are correct in standard Hindi (and I was taught as much in class 10), I don’t see why that should be a point of criticism.
Now, for the issue at hand…
Excuse me, the thing you are asking for is like, as I have said in the past, asking to change resume to résumé. (Yes, that’s the only word with diacritics I know.)
(I’ve also seen people say “resume” when they meant to say “résumé”
)
And sorry to break your bubble but, yes, people from Bihar have been dropping nuqta even in pronunciation. (I for one never use फ़ while speaking and I didn’t even know it’s pronunciation until I was forced to check it after seeing multiple usage of it in your writings. Of course, I would love to hear from you that my Hindi is “wrong” since I am not using nuqtas while speaking.) Your request is ridiculous.
I suspect most will agree to treating Bihari Hindi as a dialect. The question is what should be used on OpenStreetMap names.
As an aside, I saw the opposite problem growing up in Delhi - the most common example being people referring to flowers as “fool” instead of “phool” (and then getting chided for being “fools”
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Nuqta isn’t the only thing that have been changed, “।” is now “.” and chandrabindu is now just bindu. All these developments have happened to simplify Hindi; just pick any newspaper, say Hindustan for instance, and you will spot some or all of these changes.
Admittedly, I haven’t read Hindi newspapers in a while. I’m indifferent to the other changes you mention, since they do not affect pronunciation - but omitting the nuqta under ज or फ does. (I’m also seeing some signs omit the nuqta under “ड”…WTF!)
It’s a minor change in terms of effort, and it has a major effect in clarifying pronunciation. So I think it’s not at all “ridiculous”.
I think the only real issue is verifiability - one mapper may use the more phonetically-correct spelling, and another well-meaning mapper may “update” it to mirror the “simplified” version on the signage. Whether or not the additional clarity is worth this trouble is the real question.