its multiple directions at play, since the "cardinal directions" of the parent aren't defined by flex-direction alone. If the writing-mode of a parent block formatting context is set to a vertical mode, then flexbox' "row" will run vertically - which is why flexbox directions are "row" and "column", and can only thought of as "vertical/horizontal" in "horizontal-tb" writing mode.

Further, there's no "bottom to top" mode for horizontal scripts, but vertical modes can have a block axis running either ltr or rtl, affecting the direction of the flex cross axis. Which likely leads to the necessity to also abstract "row-reverse" and "column-reverse" directions for the ordering of items.

now as for distribution of items on either axis (whichever direction it may have), referring rows/columns when might become misleading, and also having to address individual rows (align-content) complicates things. Finding another set of terms for flexbox alone might start to become messy, since display:grid and multicolumn layouts will also require these settings.

I don't know the actual origin of align & justify either, but I have the feeling coming up with better terms might not be that easy