why are these two not equal in the sense of bound-identifier=?

#(syntax-object x ((top) #(ribcage () () ()) #(ribcage () () ()) #(ribcage
#(x) #((m1104 top)) #("i1105"))) (hygiene guile-user))
#(syntax-object x ((#f top) shift #(ribcage () () ()) #(ribcage #(x)
#((m1104 top)) #("i1105"))) (hygiene guile-user)))

/Stefan