The point was that when you do step through your program with a pen and paper, your code either do rely on the output signals already having a fixed state, or that your code start by setting them in an initial state.

When drawing with pen and paper, it may be a good idea to write an x for an unknown pin state, and a 0 or 1 when you know that the signal is low or high.

If doing that, you would notice that a change from 0 -> 1 represent a rising flank. A change from x -> 1 represent an unknown change, and is not guaranteed to produce the low-to-high clock transition that the datasheet specifies.

That is a reason why you must be methodical when writing programs, and try to write self-contained modules. And when a module do make assumptions, these assumptions must be documented. If the module assume that a signal must be low before you call the module, then that needs to be documented.