When I Post using video's URL like YouTube's, the leftside square Thumbnail is always the generic one?

Hello. When I Post by putting the video's URL, say from YouTube, the leftside square thumbnail preview is always the generic one provided by Lemmy World, the one with the the link arrow in the middle. So I simply put the URL of the thumbnail instead (eg. maxresdefault, sddefault, etc.) It's been like such since I joined.

Then just lately, I found out existing Posts in other YouTube-related Communities, the leftside square preview thumbnails do in fact show, and with the link arrow on the top-right corner instead. And I think the Body automatically inherits the existing Title and Description from the YouTube video. Both youtu.be and www.youtube.com video links work in those Communities.

Examples of YouTube-related Communities with showing Thumbnails are:

• c/youtubehaiku
• c/youtube

Here is my latest Post as example (which I have never edited yet), and I posted it via a raw Chromium profile, so no add-ons at all if they would interfere just in case:

• https://lemmy.world/post/19226604

Thanks in advance for any help.