If your wort was not filtered very well and there is considerable amount of husk fibers etc. then yes definitely you can get strong astringency from a long boil.
I know it's been asked before but has been awhile & the answers seemed old & ify so I thought I'd ask again. Does anyone have a dead ringer recipe for (my favorite) McEwan's Scotch Ale (grain preferably)?
Thanks so much, Jim.