I've packed the same icons in sbcs for three years in a row, Socrates, Ronaldinho, Zola, Schmeichel, Rijkaard and Butragueno. And in fifa 21 I've packed two mid eto'o and two mid Ronaldinho, all four untradeable. It can't be just about luck.
I've opened a lot of 5k packs since the beginning of the year, especially during the promos with the upgrade sbcs like the 81+ that keep the value of common gold players high. I haven't pack anything crazy good, a couple of 85, mendy when was at 50k and a Future star Dalot.