I've heard this argument before but here's what REI's actual policy says:
"Both backorder and preorder items automatically cancel if it takes REI more than 30 days to send them. We can extend that 30-day window if you call 1-800-426-4840 and ask us to."
To me, (1) that means it's possible for pre-orders to have been made greater than 30 days out (which is the only reason they would be cancelled - indeed this happened when I ordered my F3HR through them last year and (2) this speaks less to how REI makes decisions about when an item is made available for sale and more about what they'll do if the projected shipping date goes beyond 30 days. Even when this happens, they offer the buyer the option to keep their order (again speaking from F3HR experience)
mjulianb, I'm curious where you saw DCR's comment. I agree that what he says has reason to be reliable but didn't see it on his F5 page/comments - not questioning it, just checking that I'm not missing another source!
Amazon US has the watched marked as available tomorrow....February 21st