in this case, it’s mostly to make the negotiation easier.
instant of negotiating with a country to sell a tank and another to be allowed to sell it, they can just sell the tank.
previously there was a lot of sale that was cancelled due to the German part in it. Germany can sometimes be peeked on who can get the vehicle. even transferring an existing vehicle from one country to another still requires the consent of Germany.
but this depends on the part. many German-made parts are not regulated. but Germany is no different than any other country. USA, France, UK, Japan, Korea, and even Canada have their say on where the AFV they sell goes. it’s usually part of the deal.
now when you are negotiating the sale of a very high-tech vehicle like a next-generation MBT, you have to go through all the parts that have a regulation and tell the other country what can be done with it, where they can find replacement, who can use it. there might be thousands of parts like that and sometimes the country does not agree with the regulation or the price of a specific part so they try to change it for something else.
now imagine talking with a country, negotiating the supply, license, production, and usage of a single part with a country, and at the same time for every one of those parts, you need to go back to another country and ask them “Do you agree with that term” you have the risk to have a “no” for an answer, then you got to either negotiate with this other country or go back with the country with who you sell the tank to offer an alternative saying “I am sorry, but the term we agree is not possible, let’s start over”
do you have any idea a headache it is to sell a tank like that?
and this is some time out of pure competition. sometimes the “no” means “No, I do not want you to sell this tank because I want them to buy my tank” it happened before, and many awesome tanks were just never produced because of that despite having the prototype working perfectly well and with excellent characteristics.
it’s just easier to not have this extra complicated step to go through.
Already there is so many parts that is found in different companies that all have different regulations. you do not need to add a foreign country in the negotiation to act as an “overlord” for the rights of the parts.