Liquid chlorine (bleach) dissipates quickly despite high CYA.

I have sanitized my pool with trichlor tablets for 2.5 years. I never have any issues with sanitation. However, my CYA levels are through the roof because of this, ~100. Despite what I have read online, I have not had to keep increasing my tablet consumption. I use 1 tablet at a time until it dissolves, which is about 5 days in summer, 7 in spring/fall, and 14+ in winter. FC is usually around 3ppm according to guess-strips and Leslie's drops. I was worried that my free chlorine would get too low because of the high CYA levels, so I drained 20% of my water two times which didn't help at all. (Maybe my CYA is much higher than 100, off the charts.)
I also have high calcium (800), which was making me not want to use powder shock which contains calcium hypochlorite. Draining the pool did not reduce my calcium levels measurably either. The Leslie's Pools guy tells me to keep draining, and that local water supply is only 50 calcium.

I thought I would switch my shock to liquid chlorine (bleach 8% sodium hypochlorite) and take advantage of the high CYA levels to stabilize it, as well as not introduce any more calcium. Several forum posts indicated that it could help with both of these problems.

Last July poured 1 gallon of 8% sodium hypochlorite bleach into my 18,000 gallon pool at 9pm. It did raise my FC to 15ppm (measured 1 hour later) according to my guess strips, but it was back down to 2ppm 24 hours later.

I don't understand how 1 tablet of trichlor can last so long, but $4 worth of bleach can dissipate in one day. My best guess is that the high CYA levels in the pool did NOT stabilize the chlorine in the bleach.

Since then I have continued using my low dose of trichlor tablets (without shocking any more) with no problems in FC or pH.

Q1. Why did the bleach fail?
Q2. How am I getting away with zero shocking? Will this create latent problems?