Found problem. Spoilers in default 747 are HARD CODED to ONLY deploy at same time as reversers. You can use your controller axis or keyboard (F2) and they WILL deploy when reversers kick in.
This is a BUG (dual assignment issue) because the sim lets you assign an axis to spoiler axis but it will NEVER work as again they hard coded to reversers. Fully tested this and this applies in all scenarios.