I agree that poets should not deliberately mask their meaning and the attraction of poetry is in the phrasing.
There is another book by Mark Richardson, "The Ordeal of Robert Frost", that I hoped to find something interesting in. There was this on page 181:
Which one, after all, is the road "not taken". Is it the one the speaker takes, which, according to his last description of it, is "less traveled"--that is to say, not taken by others. Or does the title refer to the supposedly better-traveled road that the speaker himself fails to take?
So, the road not taken, could have been the one less traveled by and then there is no problem between the title and the last stanza.
I wonder what Thomas took too seriously in the poem. If his decision to enlist was a road less traveled by people of Thomas' age and family status, does this not push the meaning of the poem right back into that Marlboro-man idea of heroic selfhood that Kilgore insisted the poem was not about?