Which is why I wouldn't trust the state of the game one bit. This game is being pushed and marketed as the showcase of what dx12 can do and how much better it is than dx11. You can say that the better the game runs with dx12 than with 11 but it goes the other way as well. The worse the game runs with dx11 the better it makes dx12 look.
In game development the performance optimization is a very late task.
All that said I have no doubt that dx12 will be a significant performance boost.
As you can see here the game starts with a disclaimer
Other games running well with massive unit count? Hmm... Supreme Commander is obvious with its dx9 but a more recent example and with dx11... Wargame perhaps.
AFAIK the whole "thousands of units" thing is just a promise atm. Couldn't find footage of tens of thousands of units. Here from their FAQ:
"
How is the player expected to manage thousands of units?
Just as a military general must manage entire armies, the Ashes user interface allows players to easily take units and build "meta-units" that act together as a single, coherent, massive unit."
Why someone would want to have more than 1000 units on the screen is beyond me too. More massive than what Supreme Commander has done is hardly possible to comprehend and manage for a single player. So they morph huge groups of units into a single one.