"Crackle" glazes are technically "defects". The other name for this effect is "crazing". One person's defect is another person's feature
Whern the molten glaze freezes (glass and glaze is actually a "super-cooled liquid".... not a solid) as the kiln cools down, you have a coating of glass on the surface of a body of clay. While there is some bonding of the two (forming what is known as the "interface zone"), particularty at the higher stoneware firing ranges, they are somewhat two distinct different substances.
As the work cools, it all contracts in physical size. If the layer of glaze shrinks slightly more than the underlying clay body does, then the stress in the glaze puts it under tension. Glass is weak in tension...and so the glass cracks.... causing the "crackle" you see.
This can be "deliberate"....... and you can formulate glazes that have high expansion and contraction rates (officially called "Coefficient of Reversible Thermal Expansion). These can be rather spectacular.
Or it can be a bit incidental to the production of the work. Part of it.... but not a hugely deliberate and stressed feature. Meaning that the glaze and the clay body do not exactly fit each other...... and the crazing simply happens due to this. And the ceramist has decided that this is OK.
Some glaze formulations, because of their inherent chemical nature to get the REST of the look of the glaze, cannot be made to "fit" chay bodies...... and crazing/crackle is just "part of the deal." Anything depending on high sodium oxide and potassium oxide contents to flux (lower the melting point) of silica (SiO2) will always craze over clay.
If the fit between the clay body and the glaze is close....... often it initially emerges un-crazed from the kiln. But over time and usage, including the thermal stresses that hot tea (or hot rice) place on the wares, the glass can slowly relieve the stresses by crazing.
If the glaze actually fits the clay, no amount of hot tea or rice will cause it to ever craze.
There you have it.