The solid one allows the player to walk up it with no problems.
The jump-thru slope allows the player to walk through it from the top, which must surely be a mistake. When an object jumps up through it, shouldn't the top then act the same as the solid behavior?
.capx is HERE.
Also, there was no 'Platform 9 (jump-thru)' example when I installed R70, as referred to from in release notes.