I don't disagree that the contract will continue if Qenos can...

I don't disagree that the contract will continue if Qenos can source suitably priced ethane.
I suspect they would like to grow volumes too, which would be a big positive with the tilt toward volume pricing.
The issue is what happens if they can't buy ethane at a commercial rate.
If the SACBJV can sell it at >$8mmscf to LNG plants as part of the gas supplied to Gladstone (methane/ethane mix) Qenos will likely be facing a substantial price hike.
The risks section of the annual report spells it out, in my opinion:
- there isn't an alternative customer
- the expectation is if Qenos pulled out another party would take over the plant. This would not happen if Qenos closed due to high ethane prices. And ethane is their prime feedstock.
- the only 'plan B' is some sort of gas storage arrangement, which I would suggest is likely to produce only a fraction of current revenues.

The risk is high because EPX have no seat at the table for the negotiation betwen Qenos and the gas suppliers. So a failure to reach agreement would be a surprise sledge hammer to the EPX shareprice.

Hopefully, for all concerned, the gas supply keeps to a reasonable price, allowing Qenos to keep operating for a long time.