A couple of thoughts on this question. First of all, backing doesn't usually get much use and is mostly just a filler to flesh out the spool. In that regard almost anything will do that has sufficient strength to hold a fish should it get into the backing. It should never rot and this line appears to be dacron but not as tightly woven as the name brands. It should be more than adequate for most fishermen who rarely have a fish into the backing.
On the other hand I am still using dacron backing that is over 20 years old so longevity is not an issue with quality backing. The extra $8.00 for a known quality product when amortized over 15 years is about .53 cents a year, if it last 20 years the annual cost is .40 cents a year. Some guys will pinch pennies until they squeal, even though I am no longer a wage earner I can still pony up 40 or 50 cents a year for a known product. There is a lot of shit to worry about when you are in your mid eighties-fly line backing ain't on the list.