I buy as many pumpkins as I can when I see them and after they've been sitting around being pretty for long enough, I cut them up, de-seed them, peel them, and roast them. I then freeze them in chunks (I don't bother puréeing them at that point). I usually have enough to last me a while.
I never heard about that with the tinned pumpkin, but I always used Libby's (and never a filler or mix, just pumpkin). If you were told that by someone here, it could be they have no clue about pumpkin. Which is something I've encountered a bit here. Almost every time you look at a "pumpkin" recipe here, it's with butternut squash. It's similar, but not the same, IMO. It's just not popular here, so I think people don't recognise the difference.
Last Christmas my MiL served mashed up swede, and I wasn't sure what it was. I asked her and she said, "It's swede. It tastes like your pumpkin." I tried to explain to her that swede was nothing like pumpkin, and we actually called swede "rutabaga", but she looked at me like I was a culinary barbarian. Sort of like when I said my quiche wasn't an omelette.