This is true, however those studies are for the initial SARS-COV-2 strain and doesn't make any mention of the variants.

It's also worth noting that's a study of ~200 people. Given then times we're in it's an excellent sign and possible reason for cautious optimism and I'm sure a larger scale study is much harder to pull off in the midst of the pandemic.

That said, I have yet to see a study on the rate of reinfection of any of the variants against people who had already been infected with the initial strain, and how well that is survived, etc.