Mandatory leaf enforcement is not correct with presence container

Given the following schema:

container task-container {
list task {
key "task-id";

leaf task-id

{ type string; }

container task-data {
presence "Task data";
leaf mandatory-data

{ type string; mandatory true; }

leaf other-data

{ type string; }

}
}
}

If one PUTs:

task:

{ task-id: "123" }

it succeeds as expected without specifying the mandatory descendant leaf "mandatory-data" because its immediate ancestor, "task-data", is a presence container and it wasn't specified. This conforms to https://tools.ietf.org/html/rfc6020#section-7.6.5 (the 3rd constraint bullet below):

If "mandatory" is "true", the behavior of the constraint depends on
the type of the leaf's closest ancestor node in the schema tree that
is not a non-presence container (see Section 7.5.1):

o If no such ancestor exists in the schema tree, the leaf MUST
exist.

o Otherwise, if this ancestor is a case node, the leaf MUST exist if
any node from the case exists in the data tree.

o Otherwise, the leaf MUST exist if the ancestor node exists in the
data tree.

Therefore "mandatory-data" doesn't need to exist b/c "task-data" doesn't exist.

If one PUTs:

task: {
task-id: "123",
task-data:

{ other-data: "foo" }

}

it also succeeds. However, in this case, "task-data" is present so this seems to violate the 3rd constraint above, i.e. it should've failed b/c "mandatory-data" was not specified.