This search makes the same mistake I mentioned above - you think it finds a lot because you're sorting by "relevant" and sampling.
Sort by newest and you'll see that the vast majority of these PR's are legitimate: https://github.com/search?o=desc&q=in%3Atitle+improve+create...
The results I got show 4 spam PRs out of 10 on the first page. Same on the second and third pages. 60% is not a vast majority legitimate and 40% spam is not inconsequential when it's 86k PRs.
That doesn't match my experience. I looked at the first and 5th page from my link. No spam PRs.
Presumably the spam onslaught is slowing down with time from the video being posted so looking at the most recent results will give an ever fewer percentage of spam. If you look at page 100 of the results (for example, currently 18 hours old) there's a lot more spam.
For example: https://imgur.com/a/vxCHvcO
Here's a search that finds a lot: https://github.com/search?q=in%3Atitle+improve+created%3A%3E...