Some devs already target Steam Deck verified compatibility. Any attention to the Steam Deck helps the Steam Machine too, you'd just be playing the game in higher resolution and higher frame rate. The combined market may be more appealing to devs, but I don't see the Steam Machine selling enough to make a major difference here.

Are the Steam Machine's components good enough to run PS5 ports?

Yes, it's only slightly weaker than PS5, it's much more powerful than Steam Deck