I have to agree, braid has gone a bit down hill of late. just recently I purchased a new reel and they gave me a spool of 65lb Spiderwire Stealth, never used the stuff before always used Tuff Line without a problem..
After spooling up the sustain I run a few tests and found the breaking strain around the 12 - 14 kg right at the knot, nowhere near the 29kg you should expect.. I did however get a bit better BS when I platted and catpaws or improve albright knot it to heavier mono, started to get around the 20 - 22kg alot better but still nowhere near the 29kg it's rated at.
At the end of the day yes it isn't preforming to it stated strength but then again I don't really think I can achieve the 20kg drag on a sustain 8000 so on it stays for a bit.