Testing your results is going up have to go back to private and incognito mode, as Google points out the obvious with sites you visit often.

WordPress 5.7 to cover lazy load on iframes
A little more speed is coming to WordPress sites with several iframes and embed codes, thanks to WordPress 5.7.
Even though a caching plugin can certainly help with speed in WordPress, not everyone has one of those sorted. There are decent free ones out there, and there are those that cost money, but the simple truth is it’s not always being considered by site admins and developers.
But fortunately, the team working on WordPress might be factoring in some of the inclusions seen in caching plugins for everyone regardless of what they use, at least based on some of what’s coming.
The next version of WordPress to arrive is WordPress 5.7, and while it will update quite a bit, including more ways to edit the site using the Gutenberg block editor, there’s another aspect to get excited about from an SEO standpoint: lazy loading iframes.
Yes, this feature is reportedly being thrown into WordPress 5.7, with the popular CMS adding the tag loading="lazy"
to iframes loaded through WordPress.
For the people at home learning SEO who don’t quite understand that, it means the functionality that loads the iframe for websites such as YouTube and plenty of others don’t have to load all at once, and will only need to render in place when someone scrolls their screen to the iframe’s position. In short, it can improve the page load speed because it doesn’t have to load the element for the iframe until a user reaches it, decreasing the number of scripts that need to load on the page.
There’s more coming in WordPress 5.7, such as an easy way to migrate HTTP pages to HTTPS — which is better for security and may help SEO given HTTPS is more or less a requirement these days, plus there’s support for a Robots API to allow large image previews to be displayed in search engines.
All of that is coming in March when WordPress 5.7 is due to be released, so look out for it.