> What is high quality applications supposed to mean? Most tech jobs are simply sending a resume and maybe filling a short form

A resume for the job. Sending the same resume every time skips an opportunity to sell yourself. It commoditises you.

Not that I've applied to all that many jobs since school (a long time ago), I'm not sure I agree unless you're applying for materially different roles. I certainly agree that a cover letter should usually be customized. However, the downside of customizing a resume for each application is that it introduces the possibility of mistakes or at least less polishing. At the least it's a tradeoff.