Typical here means representative of the whole.
from the google dictionary
typ·i·cal ˈtipik(ə)l/Submit adjective having the distinctive qualities
of a particular type of person or thing. "a typical day"
synonyms: representative, classic, quintessential, archetypal, model,
prototypical, stereotypical, paradigmatic;
There is such a variety of cells in the body no one is really typical. Like a typical human. Who would that be? Me? Chinese lady? Indian kid? There are many of us and a lot of variety. Maybe you could say "typical older Scotsman" or "typical arrogant Stack Question answerer". You could definitely say "typical liver cell"; narrowing down the zone limits the variety possible and lets you more accurately characterize a call as prototypical or representative.