This could be one of those years when the historic relationship between corn and oats moves out of line. The two are sometimes considered substitutes because oats has to compete with corn in feed rations in years when demand from the livestock sector is needed to draw down supplies.
In other years, when oats is tight, it has rallied to a sky-high premium over corn. Some amount of demand for oats is highly inelastic, for example into the mills, and by certain livestock producers that will feed oats no matter what, irrespective of spreads to other feed grains.
This keeps exports and domestic demand for oats fairly steady. If there isn’t enough to go around, the price will have to do the work to reduce demand. U.S. buyers only have the choice of Scandinavian export supplies when Canada runs short. At some point the market will reflect a high enough value for them to start selling into the U.S. which will probably halt the rise in prices.