Some steps cannot start until something else is confirmed, like a hold point for a supervisor check, a gas test or a confirmation from the control room. On paper the hold is just text on a page, so nothing actually stops someone from moving past it when they are under time pressure.
In a digital procedure a hold point can be enforced, meaning the next step stays locked until the required check or sign off is recorded. Sequential steps work the same way, so the order in the procedure is the order the work actually happens in, and when someone does need to go out of sequence it becomes a recorded decision rather than something nobody knows about.