Quoting several pages back, but I'll answer this: no it isnt. Minister of defence is typically not a military leader. He/she may be able to give the military some tasks, but is typically not part of the chain of command.
The role of a defence minister varies considerably from country to country; in some the minister is only in charge of general budget matters and procurement of equipment; while in others the minister is also, in addition, an integral part of the operational military chain of command.
Usually countries with active militaries have them as integral parts of the operational military chain of command, coordinating all the Air Chief Marshals, Admirals and Generals - the Defence Secretary sets the goals and sends forth his officers to achieve them. Most of our defence secretaries in the UK have been civilians, and the Ministry of Defence itself is a hodge podge of civilians, advisors, scientists and military officials - it helps to keep things under control and in line with civilian policy, in turn keeping the military in coordination and line.
Militaries are led by whoever leads them, answering to the head of the state and/or minister of defence and/or minister of foreign affairs depending on the nation or country. Minister of defence "just" runs the ministry and is typically basically highest level the peacetime manager that has a lot to say about where the money goes over the actual military leaders.
Such managerial duties falls to our Chief of Defence Materiel and the Logistics Officers. The role of Defence Minister as coordinator of all three branches goes back to the need for the Royal Navy, British Army and the fresh Royal Air Force to coordinate under one coherent leadership during WWII - hence Winston Churchill. It's been the basic standard Western framework that's been adopted most around the world because it is necessary, and defence policy cannot be conducted by independent generals in today's world operating outside of civilian governance and coherent strategy.
We've also had female minister of defence in the 90s and the previous one before Niinistö, Carl Haglund, served in civilian service instead of armed service in the military. Great deal of people thought that alone made him an incompetent as a male leader.
You've got the same model, only your Defence Secretary/Minister is called the Chief of Defence and your Defence Secretary acts as Chief of Defence Materiel
Though you're a bit weird in that your Chief of Defence is an actual military commander, not a cabinet post