I think the reason why the difference is slight, is because we are used to hearing this in our everyday language. 'One and the same', 'the end result' and 'basic necessities' are all redundant phrases that sound okay to me, and I know I've used them in the past. And because these phrases are familiar, the tendency to believe they are correct goes without saying. Basically, if everybody else is saying it, then it must be okay. But it's not okay as far as grammar rules are concerned. And grammar is what holds together a well-written story.

Perhaps there's a regional variation and/or meaning that others might not recognize.

I'd definitely be interested in hearing the results of this! :)