That's actually very true. Obtaining the rare varieties is a long slow process, and obviously with increased rarity comes an inevitable compromise on quality, as the high grades just aren't available, even assuming you had the cash to pay for them.
With that said, I've noticed one phenomenon which isn't entirely clear to me, and that is even with the rarest coins, such as those on your rarest pennies website, Richard, there always seem to be one or two in each variety, which have somehow survived the over 100 years time span, in superb condition. Maybe the F27, F90 & F103, excepted. With less than 20, that's somewhat surprising. Does it indicate that the rarity in variety was spotted, by someone, long before Freeman spotted them?
ETA: Although you'd have thought the F90 would have been spotted as a rarity, right off the block, as it's not exactly difficult to miss at first glance.