After each wipe, does it clear the group automatically and add the new top 3 players to the group, or if left alone, will it just keep adding players to the group list?

it removes before adding the next top 3

After this last wipe, it didn't add the top 3 players to the group treasurehunter. 

Config shows:
"Ranked Ladder": {
"Award Top X Players On Wipe": 3,
"Enabled": true,
"Group Name": "treasurehunter",
"Permission Name": "dangeroustreasures.th"
},

Current ladder is clear and lifetime shows previous wipe ladder, but in console, the group is empty.

What am I doing wrong? Is there a way to force the function?

you can use /dtd wipe in game