The force working against structured reading under time pressure is cognitive shortcutting. When something is broken, the instinct is to start at the error — find the log line, trace the stack, fix the immediate cause. This is productive for shallow failures. It is counterproductive for architectural failures, where the log line is a symptom and the cause is a decision made months earlier.
The opposing force is analysis paralysis: reading the system until you feel you understand it, which never happens for complex systems. A working model is not a complete model. The question is when the model is good enough to generate useful hypotheses. F5 gives a proxy answer: when you can answer all seven questions with confidence, the model is sufficient to generate hypotheses worth testing.
There is also the organisational force of institutional knowledge concentrated in individuals. The engineer who built the system knows things that are not in the code. Getting to that person — or their documentation — is part of reading the system, not a shortcut around it.