From precedence so far and the spelling out of the incubation process, yes. It only affects the stage at which it is accepted as it is an indicator of maturity and health of a package.
Ian is correct, I recalled incorrectly from memory on the minimum requirements.
Yup, so far the SSWG has had the authors choose to post the discussion thread on their own time (since we have to find time to author the proposal and have the package in a shape for the discussion ).
When it's time for the review thread, the SSWG will make the post to officially kick it off.
IMHO you don't need to match this, but the SSWG has accepted a template format for the documented proposal. Tanner chose to essentially copy/paste his to the discussion thread, while I chose to post a subset of mine.