No, the page content is never sent to the server. all the server does is serve a static HTML page with some javascript. The javascript reads the compressed encoded data in the URL (the fragment which browsers never send to the server during a request) and then it decodes the data and writes the data to the current DOM.
All content data is stored in the link itself and never seen by the itty.bitty server.
> nothing is sent to–or stored on–this server
but isn't it the case that the entire page is sent to bitty.site as part of the HTTP request?