If I understood correctly your description: you have a metal roof secured to wooden strips installed over an existing shingle roof. During installation any upper attic / roof vents were blocked or eliminated (assuming there were some vents) and currently there’s no attic ventilation.
You are asking if there should be any ports created in the decking surface so they improve attic ventilation by allowing air to escape from the attic - under the metal roof / between the straps – through the metal roof ridge vent, is this correct?
If so, I wouldn’t do that / make such ventilation ports in any areas below the ridge line. I don’t know your geographical (climate) location, attic condition, insulation, etc. but any openings in the decking surface material could allow potential condensation from the underside of your metal roof to leak into the attic.
The ventilation should be direct, from the attic to exterior, which might be difficult to install (flashing). The only way this could work is if you can cut a ventilation channel along the ridge / ridge board. That way the attic air would be forced directly into the ridge vent. In case you have a gable / cross gable roof, you might be able to install a vent or vents on the side walls.