Ask three collectors what seasoning does and you will get three answers. One of them is about the clay, and the other two are about the ritual.
What the clay does
Zisha is fired at around 1100°C and left unglazed. The body stays porous enough to hold aromatic oils from the tea, but tight enough not to leak.
Over hundreds of infusions those oils polymerise slightly in the pore walls. The pot's surface deepens in colour and takes on a faint gloss. This is bao jiang.
What actually changes in the tea
A seasoned pot does not add flavour. It subtracts roughness — the same way a cast-iron pan softens the harshness of a high flame.
Aromatic compounds that would otherwise flash off stay in the clay and are released more slowly into the next infusion. That is why a seasoned pot makes a tea taste rounder, not stronger.
Folklore worth retiring
"One pot, one tea, forever"
Practically true, and it is about not cross-contaminating the pores. But a pot used for one type of tea — say, all yancha — is not ruined by the wrong session. Just rinse and dry.
"Older is always better"
Clay that has absorbed twenty years of charcoal-fired yancha can be wonderful. Clay that has absorbed twenty years of scented tea is mostly perfumed. Age is not a quality grade.
"Seasoning takes years"
For modern zini, a few weeks of careful use is enough to change the first cup noticeably. The deep patina takes years. Those are different claims.