Which can we infer is not what Frost intended to depict by ending the poem in a matter-of-fact tone

Are you giving me a choce to choose from?

"They...turn". Turn, in fact literally, their backs to the grave. As if to turn their backs on death; to refuse to acknowledge it. But they do not, as some suggest, return to work or play. "They...turn to their affairs." "Affairs" is often under appreciated here. What do we do with our "affairs"? We get our affairs in order, in preparation for our own death.

And what would be the next (unwritten line) of the poem? "And things will never be the same".

It would be error to infer indifference. Or to suggest that Frost in any way was minimizing this tragic loss. This is Frost acknowledging great grief and recognizing our inexplicable ability to continue in the face of it.