P: Duplicate keywords appear in the Keywording panel

When you type a keyword into the Keyword Tags subpanel that's already assigned to the photo, the duplicate keyword is added to the list shown in the subpanel. But when you type a duplicate keyword into "Click here to add keywords" box, the duplicate never appears in the list.   See here for a user confused by this minor misbehavior:

https://www.lightroomqueen.com/community/threads/lrc-15-1-sometimes-allows-the-same-keyword-to-be-entered-multiple-times.54186

To reproduce on LR 15.1 / Mac OS 15.7.1 (see the this screen recording😞

1. Start with a new catalog containing a single photo and an empty Keyword List.

2. Select the photo in Library Grid view.

3. In the Keywording > Keyword Tags subpanel, type "x" followed by return. Observe the keyword "x" appears in the subpanel and in the Keyword List.

4. Click in the Keyword Tags subpanel and type ", x" followed by return. Observe the subpanel now contains "x, x" (incorrect).

5. Go to Loupe view. Observe that the subpanel now contains just "x" (correct).  

6. Go to Grid view and type "x" followed by return into the "Click here to add keywords" box.  Observe that the subpanel above just contains "x", not "x, x" (correct).