Is type `t` still unboxed below as `t` is an abstract type?

Learning
1 
module A : sig
  type t
  val of_int : int -> t
  val print_t : t -> unit
end = struct
  type t = T of int [@@unboxed]
  let of_int i = T i
  let print_t (T i) = print_int i
end
2

This will behave as if you wrote:

module A : sig
  type t
  val of_int : int -> t
  val print_t : t -> unit
end = struct
  type t = int
  let of_int i = i
  let print_t i = print_int i
end

So yes, the type is still unboxed.