People *do* vary in their sensitivity to bitter. There are clear genetic differences in sensitivity to some bitter tastes, in part due to differences in the number of taste buds between individuals as well as over the course of a lifetime (decreasing as we age), and some people just find bitter more objectionable than others. This
Wikipedia article about tastedoesn't go into great detail, but is a place to get started if you want to learn more.
I did try the Han Zhong Xiao Han again this morning:
2 grams in 50 cc shiboridashi by Shawn McGuire, fully glazed, into Shawn’s little shino cup.
205° 1 minute
warm, vegetal, floral, delicious
205° 30 seconds
astringent/bitter, unpleasant overcooked peas taste overcoming the delightful vegetal delicacy of the first infusion, though that is still present
167° 1 minute
Tried dropping temp a bunch to overcome the effects of that 2nd infusion, and it worked a little bit, but the cooked taste is still there, more a background effect than dominating over the lovely vegetal tastes
180 degrees, 1 minute
similar to previous, with the floral/vegetal over the cooked
190 degrees, 2 minutes
Suspecting this might benefit from a ‘wake up’ hot first infusion, then immediately drop temperature a lot for 2nd infusion and thereafter.