The run/walk progression is as stated for beginners who haven’t run. BUT on those same days, you see that you can choose to either do that or a general aerobic workout. That workout can be running, hiking, and skiing under your aerobic threshold. So, if you feel like the Base plan is right for you in general with training volume and what you need, I would stick to it and just run those aerobic days and not use the run/walk progression. If you feel like you can handle more training, I am happy to switch you to the next plan up.