Thanks for your valid opinion @weirdholyman
To answer your Q comprehensively with real scenarios that took place, do go ahead & read this thread at the end here…
I’d personally rather find out about tending an allotment daily a half hr walk each way away, additional new pets, or solely looking after grandkids, mowing a huge lawn if I have a grass allergy, or as in one personal experience 2 hrs watering every single day when I worked long hours online, before rather than after committing 
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Alternatively, if something outrageous not in the WG is sprung on me last minute once I arrive, I am in a better position to say I was not aware of that duty and prefer to stick to what’s already been agreed. Not everyone likes a good showdown and some might prefer to have that back up response.
I don’t think that is a reflection of the capabilities of a sitter, but accept if you do.
Likewise I don’t think wishing to mitigate or reduce avoidable issues and potential contention upon arrival, is all that bad a skill to have as a HS…
If it’s not necessary or useful to have things in writing, then why do we have any terms & conditions or checklists at all? Let’s then just do it ALL by spoken word …
But having something submitted in writing that you are being referred to as a duty after a certain point…? 