This is the expected result that took 2 operations. Is creating one extra operation a big deal? Not at all if it were just a few per project. I am looking at literally hundreds of profiles per part so then it does become a big deal.
In my opinion NX is VERY powerful yet unintuitive. From my view this example is only one of many where the power is clearly there just not carried across.
I totally agree that we all would love to have that holy grail software and please understand it is not my intention to offend anyone here so I apologize if I did. I come from a background that cringes at anything that sounds like "that's how we've always done it".
Look into boundary geometry groups.
Operation Navigator - Geometry
Right click under your Workpiece and insert > Geometry
Type = Mill Planar
Here you can define boundaries, floor , everything you need in planar paths.
Now once you have your toolpath the way you want it you can drag and drop under new boundaries
Its very powerful and you have to remember this 2d path youa re using is very old technology.
Try to use check body with floor wall. It should do exactly what you want without any boundaries... just using wall geometry faces.
I was out for a few days and am jsut seeing this. Our users did a great job of explaining, so I only have a few general comments to add: