Hmm. He says
should and even if it was
must that does not equal to
will. On the line, everyone needs to keep checking facts against pre-conceptions. Even the correctly trained ones. Truly well spotted. I'm sure B2N2 omitted the additional "unless there are step-down fixes published" for brevity (didactic reasons).
What a peach. Dropping from FAF [D9=8900 ft - not on the picture] to the next step-down fix of 5510 [D3] would indeed compromise the OCAs. Bit of work to dive steeper than 5,3°, but it surely can be done. Those OCAs
shouldbe made into step-down fixes.
BTW it is no longer clear to me if it is lateral or vertical being discussed above under "following procedure".