Not her point.
Raids that had different difficulties (ToGC, ICC, RS, BWD, BoT, TotFW, FL, DS, MSV, HoF, ToES and ToT) ALL had a loot/boss lockout shared across all difficulties within the same “man (10/25) difficulty” (hence why you can change Legacy Raid size). If you remember how it worked then you should also remember that you could change difficulty while being INSIDE the raid. All these raids still work how they used to back in the days.
SoO does not because Mythic was introduced with WoD and during WoD pre patch SoO received the Mythic update as to get people used to it. As such SoO has different loot for all difficulties and doesnt share a loot lockout.