In any other vector software, Snap to Geometry (or snap to point, depending on the software) means anything will snap to object points or edges.
In Figma, Snap to Geometry doesn't allow me to snap a guide to just any vertex (point), only some points that are around the object's bounding box. It's even worse: some points only snap with horizontal guides and others only vertical ones, depending on the point's location. Try to snap horizontal and vertical guides to all points of a T shape, you will see the problem.
It also doesn't snap other objects to these points… Actually it doesn't snap anything! Once I deactivated Snap to Objects the guides don't stick to anything anymore.
That function is broken and it needs to be fixed.