But they are accepting signups for the waitlist (which require signing up for RH) and moving positions on the wait list based on referring other people to RH.
Even if they don't actually achieve the 3% APR checking accounts available ("sorry, it's actually 2% like the rest"), they still got people to sign up and they won't not register because they'll convince themselves "oh I got a debit card, and brokerage account, etc etc...who cares this is still great")
Though hanlon's razor makes me think this was more them not thinking things all the way through than a devious plan to get a bunch of signups without ever launching anything.
I mean that the major point of offering the checking and savings feature was to get people to sign up (both directly and by referral) for RH and make it easier for them to market trading services—and that it was serving that feature without being launched—not to argue that they planned never to actually launch the feature.
Their website says "Robinhood Checking & Savings is launching early 2019."