Rye::Box vs Rye::Set

irb_session.txt

irb(main):001:0> b = Rye::Box.new('172.22.1.111')
=> #<Rye::Box:172.22.1.111 name=172.22.1.111 cwd= umask= env="" safe=true opts={:port=>nil, :keys=>["/home/rwh/.ssh/id_rsa"], :paranoid=>true} keys=["/home/rwh/.ssh/id_rsa"]>

irb(main):002:0> b.uname
=> [Linux, , 0, ]
# ok, works as expected

irb(main):003:0> s = Rye::Set.new
=> #<Rye::Set:default parallel=false opts={:user=>"rwh", :safe=>true, :port=>22, :keys=>[], :password=>nil, :proxy=>nil, :debug=>nil, :error=>#<IO:<STDERR>>} boxes=[]>

irb(main):004:0> s.add_boxes '172.22.1.111'
=> #<Rye::Set:default parallel=false opts={:user=>"rwh", :safe=>true, :port=>22, :keys=>[], :password=>nil, :proxy=>nil, :debug=>nil, :error=>#<IO:<STDERR>>} boxes=[#<Rye::Box:172.22.1.111 name=172.22.1.111 cwd= umask= env="" safe=true opts={:port=>22, :keys=>[], :user=>"rwh", :password=>nil, :proxy=>nil, :paranoid=>true} keys=["/home/rwh/.ssh/id_rsa"]>]>

irb(main):005:0> s.uname
Passwordless login failed for rwh
Password: IRB::Abort: abort then interrupt!
# why does this behave differently?  how can I make it behave like Rye::Box?