I think it's overly pedantic. Imagine trying to pull up someone for that in a Court of law. The judge would laugh at the ATO for being ridiculous. Sure, if you leave it in there for a long time then it loses that nexus between the borrowing and the expense - but not for 1 minute. There is definitely a reasonableness test that applies in these situations.
I agree in part. But it is best to do things properly to avoid doubt.
If ever money is drawn and placed in a savings account with other money then the loan interest on this amount will not be deductible. There is case law on this. Domjan is the case. Paragraph 42 specifically . From memory.