Yeah the Chlorox label claims 100% CYA. Always figured that's what I'd use if it ever came to that.
But it hasn't. I really like the trichlor method of maintaining CYA, too. For 20K gal each puck is 1.7 ppm. So a floater with 4 pucks is about 7. When water is 60F and below (we don't close) the vents can be set so that lasts just about a month with FC at TFP target. Starting mid-August (now), let CYA drift down toward 60 with natural loss. Then get through all or nearly all the cold months with trichlor. In spring it's at 80 again to turn the SWG on. If 80 comes too early, then it's LQ for just a few weeks. For summer vacation, load up the floater again. The CYA boost offsets normal warm weather losses and FC is insurance against SWG hiccups. This method has taken us through 4 summers never yet buying CYA and always in the 60-80 range. Other nice stuff: when the floater is in, don't need pH adjustment (down) at all, and SWG life is being extended.
I kind of fell into this method because I bought a bucket of pucks before finding TFP. Had to use those somewhere. It worked out so nicely, it just made sense to keep on. Ymmv. Every pool is different.