[vannevar]

I think you've answered your own question. Between working one hour out of the day, or ten minutes out of each hour, which is actually more feasible and likely?

In a day rate situation, if you're blocked by client inaction, they're still paying you daily. In an hourly situation, that is generally not the case. And if you can truly satisfy client obligations working only an hour a day (very unlikely), then yes, you'd still get paid for the days and there would be nothing unethical about it.

[beagle3]

Yes, I answered it - and in my experience, and I do have relevant experience, it’s not acceptable unless (a) blocking and (b) properly agreed and documented in the agreement that downtime waiting for client is billed at full rate. YMMV - either way, unless blocking is common, the day rate vs hourly rate is just a change of unit. Blocking is not common in well run projects I’ve been involved in, and not even in those that were badly run (though more than the well run)