I investigated the issue in the post below further. I found that this may be because all comments were removed during the simplification process. When I changed the configuration option to remove comments to false, I was able to generate an HTML file that could be imported normally. Is this related to the HTML structure?
I seem to recall seeing somewhere before that comments in JavaScript code appear to have a special purpose.
Usually comments have no impact on JS code. TW-modules do have a header that is similar to the .tid meta data. But these comments are all hidden inside the TW core-plugin. So they are not responsible to import the wiki-store, if you do a drag and drop import.
/*\
title: $:/core/modules/....js
type: application/javascript
module-type: global
Some info ...
\*/
The modern wiki-store is a SCRIPT tag with type=“application/json”. This script tag is used to identify the start and end of the tiddler store.
<script class="tiddlywiki-tiddler-store" type="application/json">
The only difference I saw was that your script tag looks like as follows. As you can see, it misses the double quotes.
<script class=tiddlywiki-tiddler-store type=application/json>
If you add those quotes to your file, it will be possible to drag&drop import it. → I did test that.