"Traditionally, testing was often relegated to the final stages of development, just before the release"
I was going to dismiss this as another strawman - the same strawman that we've been whipping since Winston Royce, 1970.
But then I see:
"At the outset of a project, during the planning phase, testers should collaborate with developers and stakeholders to understand the requirements and define clear, testable acceptance criteria."
How did we get back to waterfall?