Tongue groove wood flooring - oops, I cut them both off
The risk is that the boards will become unflush during seasonal expansion and contraction. Even if they look fine going in; tripping hazards will appear at these seams once everything settles (and then unsettles... and back again).

I use a table saw with three blades sandwiched together to cut grooves back into my useless cut-offs. Tongues aren't fun to make, so just use tongueless ones against the wall, cut again to fit. 

You can start each row from either side, so long as the cut end goes (spaced, for expansion) against the wall, and you have at least one tongue or one grove.