Same reason a ton of us pay for AWS/GCloud/Azure instead of dealing with bare metal. (And I say this as someone running an edge fleet. If I didn't need to, I wouldn't.)
What you describe sounds more like a cleverly hidden ad. Google and others were famous for this during silicon valley's growth phase when you could get a job as a software engineer if you had heard of Java in passing and could fog a mirror.
Intent matters: a hiring campaign doesn't rise to the level of poaching unless there is some concerted effort to attract specific employees and/or talent from a specific company.
Finally, poaching is a perjorative term, but the practice of hiring another company's talent (even if they are a competitor) is not illegal or unethical. Companies SHOULD have to compete against each other for top talent.
Maybe a little distasteful since I suppose since these WordPress sites are not owned by WordPress, but I wouldn't really say it's unique or necessarily poaching