Ann: Notice of General Meeting - Leo Lithium Demerger, page-82

You have pretty much summed it up:
~ The previous placement shares were issued without shareholder approval as they did indeed fall within the Listing Rule 7.1 & 7.1A
(15% and 10% capacity rules) and by ratifying the placement shares it resets the 15% capacity allowance.
~ Voting against the resolution, means that if the want to issue shares it they will be subject to shareholder approval, and can have an inhibiting affect on their ability to raise funds. Sophisticated investors and 708's want more certainty than be at the whims of shareholders.

The 15% Capacity is from memory is from point in time, and only available for a 12 month period,
~ shares issued *as in the case was 17th December 2021 (without shareholder approval, falls under the 15% capacity rule) means the 15% doesn't get reset again until 16th December 2022, thus by having the shares ratified it gets reset on the day of meeting.

As for better transparency, no in particular, if the Company want to have a placement, it is very rare that they inform shareholders prior and also,
if they do go over the 15% capacity it is rare that shareholders wouldn't approve it.

cheers