I am not a Leica or Panasonic Manager. I do not know what kind of agreements have been made. But what we can guess is, that the Q body seems to be developed by Panasonic like every modern Leica camera.
But for the first time, there is no similar product with a Lumix lable on it. Same for the Leica SL3.
This is not by accident in my view.
Leica can not control, what Sony does. Probably even not what Sigma does although they are founding partner of the LMount alliance.
But they can control Panasonic. If Leica places an order for a specific product, they can write into that contract, that Panasonic is not allowed to offer something similar. Even if it has not a fixed lens.
I do not think that Leica has this kind of control over Sigma, although Sigma made many lenses for Leica, because Sigma is in a better bargaining position. Sigma sells a multiple of lenses in other mounts.
I hoped for many years for a Lumix Q camera, but it did not happen. Same for a Lumix GX9 in fullframe. Many costumers ask for these Lumix products, but Panasonic refuses to offer them.
Panasonic is not stupid. They would not turn down an offer to make more money. This is why I think that there are other agreements which holding Panasonic back.