Should I "sponge" tea?
Rinsing tea is normal in a ceremonial preparation of tea. There can be several reasons for rinsing:


To wake up the leaves: Especially with tightly rolled teas, the infusion is more optimal when you let them unfurl a bit during a short rinse.
Remove unpleasant flavor on the surface: With some roasted oolong teas or pile fermented teas, the earthy or smokey flavor on the surface can be unpleasant. So people like to rinse the first layer of flavour away.
Remove impurities: There's a lot of processing steps involved to produce a tea. And when the environment isn't kept clean, the final tea may not be clean. I personally always rinse ripe pu erh tea and oolong tea. These teas have the most chance of being 'dirty'. I don't rinse green, black, raw pu erh and white teas.