Users are unable to load Dropbox choose SDK on the Safari browser

I am trying to load Dropbox choose SDK on my website. But running in to an issue on Mac Safari browser.

<script async="" src="https://www.dropbox.com/static/api/2/dropins.js" id="dropboxjs" data-app-key="crbrplpove29sb2"></script>

but script doesnt load on xconvert.com (if you goto the network tab and load https://www.xconvert.com/compress-mp4, it won't show dropins.js). I also tried manually injecting the script to the header once the page is loaded

const node = document.createElement('script');
node.src = 'https://www.dropbox.com/static/api/2/dropins.js';
node.type = 'text/javascript';
node.setAttribute('id', 'dropboxjs');
node.setAttribute('data-app-key', 'crbrplpove29sb2');
node.defer = true;
                          
document.getElementsByTagName('head')[0].append(node);

But same code on other websites such as smallpdf and ilovepdf seem to work perfectly.

There is a preference on Safari, under Privacy saying 'Prevent cross-site tracking'. If I turn it off, then the script loads perfect on the xconvert. But that setting don't need to be turned off for other websites I mentioned above.

Any idea what may be causing this issue?

It almost feels like Apple whitelist some website and block others from loading third-party scripts. This only happens on Safari. It works fine on Chrome.

Safari version: 14.1.2 Mac version: 11.6

Following is the error thrown on script which is not much helpful https://discussions.apple.com/content/attachment/04520a01-1b75-45e2-9fc4-039e7c1c9a9b