Since mesh is introduced, prim count is changed.
This makes is possible for simple objects (shapes), which are linked together, the prim count on land impact to cut in half.
So when an object does have a comlex shape it will not work.

Try this inworld:
1. Create 2 cubes and link them together and watch the prim count on land impact.
2. Right click on one cube and select "Edit".
3. Select the "Features" tab.
4. Change in the "Physics Shape Type" in the drop down menu from "Prim" to "Convex Hull".
5. Now watch the prim count on land impact again.

Disadvantages are:
When physical state is not "Phantom" and "Path Cut" is used, it is not "Walk through" like it seems to be.
Which means that you can bump into a wall that is not even there.

This can be used for example on a picture frame with no problems.

How to reduce one prim on a picture frame:
1. Right click on the picture frame and select "Edit".
2, Select the "Features" tab.
3. Change in the "Physics Shape Type" in the drop down menu from "Prim" to "Convex Hull".

The 3p Version of the Picture Frame becomes 2 prims.
The 2p Version of the Picture Frame becomes 1 prim.
For the 1p version, it makes no difference.

I hope this information is sufficient.
Good luck and have fun.
Greetings, Ydille.