i dont exactly get it. when i caught Xern(to lazy to type Xerneas...) xern had 3 PERFECT IVS!(HP,ATK,DEF) im a bit sad with IV spread, but, 3 IVS!!!! ON A LEGENDARY!!! COMPLETELY RANDOM!!! NO SRS!!! so do all legendaries you encounter have at east 1 or 2 or 3 perfect IVs? can someone just tell me!!
All Legendaries have 3 IV's like the other said. It also seems they have a higher chance to get 15+ IVs in each stat. Randomly caught a Latios with 5 31 IVs and a 25 as the last one. I haven't heard if this is officially a thing, but most of my legendaries have had all stats with 20+ IVs.