Hi and welcome to the forum! Shipping has been discussed ad nauseam lately and there’s just too much to really cover. Basically no, it’s not random, but it’s not as simple as going by order date either. We don’t know the exact criteria GF is using though so much of what you’ll read is speculation on how they are going about it.
Here’s the discussion jrnelson mentioned. It has a lot of info and the spreadsheet
