Why would this be? The only physics we know is the one inside our observable universe, there could be variations beyond, or even unknowable laws that don't require conservation of matter outside the edge of the universe.
Our incredibly vast universe could be a minuscule blob feeding from an incredibly vaster parent universe, in which case it could be breaking conservation infinitely from our perspective.
I suppose we're like bubbles on a boiling pot of water when the fire stops: all this agitation spreads out on the entire volume, and sure no energy was lost, but there are so little bubbles and so much water, once the heat has spread out entirely, the whole volume of water looks pretty dead.
It is constantly transforming, but that does not signify that it was created, that is beyond the evidence
Also this discovery does still is being explained with dark energy (albeit time varying …) so it still does not assume global energy conservation.
My favorite quote:
> I like to think that, if I were not a professional cosmologist, I would still find it hard to believe that hundreds of cosmologists around the world have latched on to an idea that violates a bedrock principle of physics, simply because they “forgot” it. If the idea of dark energy were in conflict with some other much more fundamental principle, I suspect the theory would be a lot less popular.
Because there is no shortage of 'crackpots' that have 'obvious' solutions to unsolved physics problems, and that want to publish papers about it.