New swatch with the incremental number is added after find/change text between different files

I made a screen recording. My OS is OSX Sequoia 15.5 (Apple M2 Max)。 But this bug(?) can be reproduced on other versions of OSX as well.

My steps:
1. Quit InDesign 2020
2. Open a.indd and b.indd files (even if you only open a.indd first, and then open b.indd after color retrieval and replacement, you will encounter the same problem)
3. Find and replace on a.indd: 1. keyword :test; 2. font color: red; 3.scope: document (not all documents).. Execute the replacement. 
4,Close a.indd. (If you quit the indesign app, you won't have the problem I mentioned)
5,Repeat 3-4 on b.indd.

I initially found this problem in my code, which is as follows (probably the code is easier to understand than what I'm saying). 

var files = [
    "a.indd",
    "b.indd",
];

var curPath = new File($.fileName).path;
var len = files.length;
for (var i = 0; i < len; i++) {
    var doc = app.open(new File(curPath + "/" + files[i]));
    var redColor = doc.swatches.itemByName("red");
    var tf = doc.textFrames.itemByName("*****");//target textFrame: **edit this
    changeKeywordColor(tf, "test", redColor);
    doc.close(SaveOptions.YES);//close document
}

function changeKeywordColor(textFrameObj, keyWord, colorObj) {
    app.findTextPreferences = NothingEnum.nothing;
    app.changeTextPreferences = NothingEnum.nothing;

    app.changeTextPreferences.fillColor = NothingEnum.nothing;
    app.changeTextPreferences.fillColor = colorObj;//red color

    app.findTextPreferences.findWhat = keyWord;
    textFrameObj.changeText();// Search scope: only the target textFrame
}

Thanks.

I've tested both the IDML file and the InDesign file converted from idml, and they both have the same issue. These files were created in InDesign 2020, but based on my testing, this problem exists in all versions from 2020 to 2025.