Ok, I figured out what was going on here.
Razix actually has two sex scenes with Yoshi, in Chapter 6 and Chapter 10.
If your choices bypass that first time in Chapter 6, at the end of the story, you'll get that one instead of the second scene. And the first sex scene doesn't have a CG yet.
To get the first scene, you'll have to have oral in Chapter 5, otherwise you get the oral scene in Chapter 6.