Thanks for bringing this up!
The subject of a re-review came up in our last meeting, and we are planning to do another round very soon! Per the process documentation we are supposed to do this every 6 months so apologies for the delay.
And yes, we can/should provide transparency around the decisions to maintainers. We make decisions based on the incubation process criteria for each level, so generally if a package was not promoted it's because one or more criteria for the next level were not met, but it might not be obvious in many cases which of the criteria those were.