Buyers are told to DENY a cancellation request if they have not received the refund

It is far better to hold off on the shipping as the buyer asked.  Not uploading tracking within the stated handling time is fine -- it is not required and no "defect" results.  The 90% deal is not relevant to most sellers.

It is highly unlikely that the buyer will complain about a "delayed" delivery that he/she specifically requested.

In other words, stop being so paranoid and just do as the buyer asks.

I can't imagine not thinking ahead, ordering something and then making that the sellers problem

I can, if it's a rare or hard to find item the buyer doesn't want to miss out. This happened all the time in the good ole days when ebay was the place to go for things you could find nowhere else. Back then the buyer payed and the seller shipped when the buyer requested and everyone was happy. Now it's a big drama, but you can't blame the buyers they are just buying stuff and making simple requests. The drama comes from mama ebay.One late tracking ding (not a defect)  is really not an issue for most sellers with any volume at all.

I hold packages all the time. It's good business. A month is a bit longer than usual, and I personally would still hold the item, but an alternative would be for you to contact the buyer (thru private email--if they have paid it's on paypal) and ask them to request a cancellation as ebay won't let you hold items any more once they are paid for. Then I would offer to hold it for them in your inventory for that month.