There appears to be a bug with Mythic Sylv and Jailer - If you run it with a 20M raid you will see 4-6 pieces of loot; the amount appropriate for a 20M Raid.
If you run it with 5 or less you will see the amplified amount of loot that you should.
This is able to be reproduced fairly easily, and seems like the posts claiming “Do it with under 5” has merit.
I’ve seen a lot of posts in General forums filled with keyboard warriors talking about ‘git gud’, and preaching incorrectly about probability so I wanted to make a specific bug ticket for it.