Since 70% of the stem is on the original steerer and the 30% left is on the extension once torque it is very unlikely to happen
Plus the top bolt of the stem is right ont the transition and will help holding everything together
With no bearing cap it was possible to ride the bike without the extension and 3/4mm of the stem above the steerer but for my peace of mind I prefere this way
Since 70% of the stem is on the original steerer and the 30% left is on the extension once torque it is very unlikely to happen
Plus the top bolt of the stem is right ont the transition and will help holding everything together
With no bearing cap it was possible to ride the bike without the extension and 3/4mm of the stem above the steerer but for my peace of mind I prefere this way