unsafeRandom isn’t flagged as unsafe for the reasons you are stating. It is probably easier to explain with an example.
It is very easy and very likely for a contract writer to write a contract where the randomness is generated in the same transaction where the value is delivered. Say in a pack situation if what was in the pack was decided at random during the purchase, I could in theory write a transaction that buys the pack, opens it, and only completes the transaction if the delivered nft serial numbers are to my liking. I could then run that transaction say 10 or even 100 times at once, so that I am more likely to receive a valuable pack and guarantee a bag of valuable nfts at the small additional cost of gas for transactions that weren’t up to my get rich quick standards.
You can then say, well just make it so the randomness is decided in a different transaction to the delivery of the value, so that the sale can’t be stopped if the purchaser doesn’t like the outcome. Which is correct, and I believe the answer to the question @zach8302 asked.
Be super super super careful with randomness and blockchains.