What IS it about Red Zinfandel? ? ? Help!

[quijote]

The bitterness of tannins attributed to wine here sounds like the puckery and bitter "tea-bag" effect of tannins in overbrewed tea.

Beyond texture and grain size, are all tannins basically alike? Are wine tannins basically the same as tea tannins? Or are they different in other ways, due to their different origins (seeds and skins in wine versus whatever creates tannins in tea)?