The short answer is that 155° (for breast meat) is moist and still has a good texture. The USDA recommends cooking chicken to 165° because it's easy to remember, and at 165° bacteria has been eliminated, and pasteurization has occurred.Looks amazing! I'm genuinely curious on why you SV at 155 vs 165?
The long answer is sous vide uses a combination of temperature and time to achieve pasteurization. So... Chicken cooked to 155°, then held at 155° for 1-minute will be pasteurized. Chicken cooked to 152° and held for 2-minutes will be pasteurized. This method of temperature and time is called a 7-log 10 reduction, and is approved by the USDA. Restaurants use this to some degree. This article explains this using baked chicken, but sous vide gives me better temperature control.
Baked Chicken Breast Recipe: Thermal Guide Plus Salsa Verde
Baked chicken breasts are a great quick dinner, but it so often turns out dry & rubbery. With a few tricks and some critical temperatures, you can have tender juicy chicken every time.
blog.thermoworks.com