I agree.

There are two separate terms which people seem to be confusing - "oversold" and "positive space". Those things are different.

At the risk of getting these definitions wrong....

Oversold means that AC will no longer sell any seats on the plane. Everyone seems to agree that the flight in question is *not* oversold.

"Positive space" means that they have sold fewer economy seats than they have on the plane.

The difference is that they can predict (with surprising accuracy) how many people will show up for a flight (taking into account missed connections, flat tires, people asking up ill, etc).

They can also​​​ predict (with surprising accuracy) how many people they can accommodate on a flight (taking into account the fact that they may have unsold J and PY seats).

If the number of people who they predict will show up, is more than the number of people they predict they can accommodate ... then they won't sell any more seats for it. That flight is now "oversold".

​​​​​​​If, however, they have sold 201 Y tickets for a plane that has 200 Y seats - but there are also 7 open J seats, and they predict they will get 4 no-shows ... then they believe they can accommodate everyone still - in fact, they will continue to sell more tickets. That plane is *not* oversold. However, because they sold more tickets than Y seats (in this example, 200 ticket), it does not have "positive space"

​​​​​​​A plane needs to have positive space for them to offer IKK to it. My example above is not oversold, but does not have positive space, and so you would not be able to IKK it.