I think you're reading the sentiment backward. Of course Ukraine wants stronger sanctions against Russia in any case, because an invasion already happened, not because they believe a full-scale invasion will happen.
They explicitly say (including in the tweet from the FM that I cited) that strong action now is important because Russia’s future action depends on what other countries do now.
Yes, they think an invasion already is ongoing, but that's explicitly not the only factor in their call for action. It is directly tied to impact on Russian escalation.
