No, it has never been that way.
The bundler adds some convenience import configurations if it is installed, but bundles have always been compatible with the standard TW JSON export / import format.
The bundlers initial way was to create a JSON file and import it into a new wiki.
With the plugin version v0.5.0 from Feb. I did add the new draggable icon as shown in my first post, which has very similar code as the core tag-pill.
I think you do use a very similar code for the Drag-Tag too.
The cool thing is, that TW tag pills can be dragged to the browsers “Bookmarks bar” from where you can drag it back to every TW. – We only need to figure out, how we can give the initial bookmark a better name then data:text/vnd.tiddlywiki...