Near Osnap and .x .y .z lacks precision

Rhino
1

Near Osnap on.
Create a curve or a line which is not parallel to the x axis.

Start Point command.
Move the cursor near the curve or line. The point snap to the curve or line.
Click to complete the command.

Start Point command.
Type .x and then a value of x which lies on the curve or line.
Move the cursor near the curve or line. The point is constrained to the set value of x. However the point does not snap to the curve or line. The cursor snaps to the curve or line and the point will be at the set x value and the y value of the cursor on the curve or line. The point will not be on the curve or line.

Using .x .y or .z to place a point on a curve, line or surface will usually result in a locaton not on the curve, line or surface.

2

I think that what you want is that the point snaps on the curve at the intersection of the line through the points’ x position with said curve. You could achieve that behavior with the use of Int Osnap and Smarttrack