The text “can block as though it had flying” does not exist on any cards any more; any cards that used to have it, such as Canopy Spider, have received errata to have Reach instead. Note that even Giant Spider was printed at one time with the “can block as though it had flying” text.
When determining the correct card text of any card, all that matters is what is written in the Oracle card database at gatherer.wizards.com. It does not matter which printed version of the card you are playing with.*
However, to answer your question in terms of MTG history, back when those cards did have that text, yes, they could block Treetop Rangers. This is because for the purposes of declaring them as blockers, you acted as though they had flying. The errata to use Reach changed this interaction.
Creatures with reach (and without flying) won't be able to block creatures that say they "can't be blocked except by creatures with flying," simply because those creatures don't actually have flying (and will no longer act as though they do). Cards affected by this change are Elven Riders, Silhana Ledgewalker, Treetop Bracers, Treetop Rangers, and Treetop Scout.
*The un-card R&D's Secret Lair aside.