Mostly I'm just thinking about this from the IndieWeb "Own Your Own Data" perspective, so if I'm reading this all correctly, the way the plugin is handling things, it's relying on Twitter's long term existence to serve up the physical content of the tweet?

I would suggest that using the blockquote method with the associated .js may be preferable for IndieWeb users as it saves the content of the tweet as a blockquote with the associated metadata. At worst, if Twitter disappeared, then one would at least "own" the text of the original which would minimally fallback to display as a simple blockquote rather than the fancier embedded Twitter card.