As far as I can tell, this isn't an issue with resizing or the add-on. XenForo's default style limits iframes' height to 150px inside of quotes. This is from bb_code.css:
Code:
.bbCodeQuote iframe,
.bbCodeQuote .fb_iframe_widget,
.bbCodeQuote object,
.bbCodeQuote embed
{
max-width: 200px;
max-height: 150px;
}
I guess you could remove that block if you don't like it. Otherwise you can selectively remove this limit by adding this to your EXTRA.css:
Code:
.quote>iframe[data-s9e-mediaembed="twitter"]
{
max-height: none;
}