I checked the randomness of loot containers a few weeks ago. Was working fine. 75% of 1 means you have a 75% chance to get 1 and a 25% chance to get 0. That also applies to any partial amount. 5 items on 50% loot means 2.5 items, so a 50% chance to get 2 or 3.
There was this change: "Change "Boss Volume" to "Quest Exclude" on sleeper volumes", which repurposed the boss volume flag we never used to allow designers to exclude volumes from a quests requirements. Like a garage outside a house could have sleepers in it but not be required to fulfill a clear quest.