Snap always full height

On your onboarding example, while holding the snap shortcut, you can move around and choose either height or width size or both.
On my screen it's only width size. I do not have an 8 square grid or even 4 square grid. I did put a left outer gap to keep my widget visible. Is this related to the issue ? or did I misunderstood the way to use the snap assist ? In layout & Gaps settings I even reduced the Minimum window height and width to 50.