It's a frequently asked question.
A big clue as to how W5R3 works, can be found in this slightly-similar-to-C25K 9-week 'return-to-run' protocol (Week 10 is 3x 30 minutes), for anyone who's maybe coming back from injury and lost a lot of conditioning. Like me
See if you can spot that big clue. Answers not on a postcard, but via reply below