Validation means checking the job with the people who would use the first version. Talk to them before you commission screens of every idea. Ask what they do today, what they abandon, and what would have to be true for them to switch.
A clickable journey of the core task is enough to test the idea. A full build is not. If the conversations disagree with each other, the idea is not ready. The disagreement is the finding.
Sovassa treats that check as part of framing the product, not as a separate workshop with no consequence for the scope.