Then why have a circling minima at all?
You could just fly the runway aligned approach down to its better minima, and if visual off that, circle in the day with your 300/400 feet. Are you telling me that I could fly an ILS down to visual @ 300 feet, then break off and circle (assuming 0 ground elevation and no obstacles)?
The regs in that section make a distinction between night and day for all other aspects of the visual approach and descent below the MDA. This particular reg doesn't however, strongly inferring that there isn't one. Whilst a CASA FOI certainly isn't the final authority on this, I asked this question yesterday and got the response I expected.
As the reg says, unless the landing can be affected from conditions equal to or better than the circling minima, a missed approach must be conducted. And by conditions, all conditions. Vis and cloud base. I understand that common sense suggests otherwise.
And for the love of god keep the self righteous abuse of others with a differing opinion to yourselves. I know we all like to think we are the final authority on everything aviation but its unnecessary.