D,
I struggled with this question for a long time. If you were to audit my answers, you’d find that I’ve evolved (or maybe devolved) over the past 10 years.
Here is my current position (which may change next week):
Extra-curricular, non-specific activity should be factored in when selecting a plan level. It should not be counted as exercise volume in your plan.
So, 12 hours a week on your feet should dictate whether you choose Level 1 or Level 2 plan, but you should not count your dog-walking as exercise time toward the plan you choose.
There is defiantly fatigue caused by walking, lifting and standing. It can significantly impact your ability to train. Unfortunately, the fitness benefits from this auxiliary exercise, while helpful to overall health, is not very helpful for endurance exercise.
Ask me again in a year and see what I say then!
David