The following command may remove UUIDs from collections, even if in 3.6 FCV:

db.runCommand({applyOps: [{ns: "test.$cmd", op: "c", o: {collMod: "col"}}]})
{ "applied" : 1, "results" : [ true ], "ok" : 1 }

2017-11-30T11:38:12.809-0500 I ACCESS [conn1] Successfully authenticated as principal sajack on test
2017-11-30T11:38:16.371-0500 I COMMAND [conn1] Removing UUID 3bf5c40d-a25a-478e-bb91-fb6f762d504c from collection test.col