I guess that there are a couple of things to consider here.
1. if you did initiate the evacuation command before you actioned the checklist, will the passengers sucked into the running engines thank you?
2. If you do an analysis of the number of flights per year, and the number of uncontrollable engine/airframe fires - particularly those that end in a pax evacuation, I suspect that you would find that it is a discussion that isnt worth having
3. why second guess the procedures as specified by your company? what makes you think that the people that wrote the procedures are dopes that missed the obvious?
To answer your question about why change the procedure - it is a fact that recall checklists, when conducted under the stress of a real emergency, are more often than not carried incorrectly - in many cases it might be only a minor deviation, but nevertheless incorrectly.
Changing those procedures to "read and do" forces people to slow down and think about what it is they are trying to achieve, and provides an opportunity for a means to stop people missing things in the heat of the moment.
The sim isnt a real test of reactions in the real situation - regardless of the fidelity of the sim people still know there is no risk....