I think the change occurred because of someone's request on his recent Twitter spaces discussion about the algorithm release. Near the end a participant asked about the "Fail Whale" being brought back because it had personality and she missed it. He said he would see about it. So perhaps he wanted to find out what the process would involve for modifying the site's logo.
Edit: tineye shows only one source older than dogecoin https://tineye.com/search/db05d61c3c1a85f0422ce55961c83e0a59... and I don't think Elon was thinking of blowoutcards.com.
If it was the 'Dogecoin logo', you would have a point. But it is an image of the doge meme.
>Elon Musk’s Doge barks up SEC’s tree
https://www.reuters.com/breakingviews/elon-musks-doge-barks-... (via https://news.ycombinator.com/item?id=35461807)