No, the endwall can't match the slope of the pipe. All structures come in completely vertical (yeah, I know).
If the insertion point is at the start of the end section, you can't call out a stake-out point at the end of the end section. The only elevations you can call out on a structure is rim (top of end section at insertion point), and the pipe elevation with the text for each component under the insertion point.
But you could get creative by placing a pipe instead of an end section for the length of the end section to match the slope of the incoming pipe. Assign a no plot style. Make sure your rules aren't forcing it to drop vertically. Place pipe labels on it calling out its end elevation for stake-out. Then insert a block over the top of it to achieve proper symbology.
