They probably have an update for DLC #1, that might be why your getting that message. Because DLC's also get updates and bug fixes.
Well it's seem there is an update for the game (v144) and for the dlc (v64).
If i remember well, here is the history of the updates of LOZBOTW :
21/02/17 v0 initial disc game version 0.9 + update v16 initial disc update version 1.0.0
03/03/17 update v33 version 1.1.0
31/03/17 update v48 version 1.1.1 dlc 1.0
11/04/17 update v64 v16 extension pass version 1.1.2
01/05/17 update v80 v32 language pack version 1.2.0 (FREE DLC for the swapped tik trick...botw without cfw)
29/06/17 update v97 v48 dlc#1master trials version 1.3.0 dlc 2.0
07/08/17 update v112 bug fix version 1.3.1
08/11/17 update v144 v64 version 1.3.3 (FREE DLC xenoblade 2 quest) dlc 2.1
21/11/17 update v160 bug fix version 1.3.4
08/12/17 update v176 v80 dlc#2Champions ballad version 1.4.0
15/12/17 update v192 bug fix version 1.4.1
31/01/18 update v208 bug fix+language add version 1.5.0