In a word, yes. The braid is hard, slick, and unforgiving. The mono backing will help cushion the spool from pressure and tightening of the braid. It will give the braid something to grip on to when the braid is tensioned, and wants to slip. On reels not designed to fish straight braid, sometimes the whole lot of line will spin around the spool, or lower layers of itself. Also, braid is very thin, and it will usually require you to put a whole lot more on the spool than you will ever need, wastig money and line. If you put it on straight and keep cutting back, eventually you will be fishing w\ a very small diameter, but lots of line. Better to put enough on to fish, the after a few cut-backs, either splice on some more or replace it.
Paul