Why did some Galaxy M16 5G's come with One UI 6.1 instead of One UI 7?

I just bought a Galaxy M16 5G which is supposed to arrive with One UI 7. While some units shipped out with One UI 6.1 for some reason, including mine.

Why is it so? I do know that some M16's run One UI 7.

Apart from that, Some things like Video Resolution are downgraded it seems. M16 has FHD 30FPS as max, while my cheaper M05 has FHD 60FPS.