IN I-69Whe: Exit 20?

[yakra]

I  I-69Whe Exit 20 is shown as Exit 21 in OSM and Google.
The weird bit is that it was originally labeled 21, and relabeled 20, based on the AltLabel of 21 in both the I-164 and I-69Whe files on CHM, which are dated 17-Aug-2014 18:08.
More recent GMSV imagery, dated Aug 2015, still shows Exit 21 signed in the field.
(I wonder if maybe the person making the edit hit "Add Alt. Label" rather than "Demote" in WPTedit...)
Should these labels be swapped, with 21 becoming the primary label, and 20 demoted to the AltLabel instead? Or am I missing something?

[mapcat]

I didn't draft the file, so I'm not sure where the 20 may have come from. In any case, it's exit 21 now, and according to GMSV it has been since 2009, before the road became I-69. 21 promoted/20 demoted in my file.