You must have misunderstood what I was saying.
I was just pointing out that IF you were to somehow allocate an actual cash value to the time that you spent on the pro bono work in order to come up with a figure to claim as a tax deduction for doing that work then you would have to account for that amount as income for the work in order to be able to claim it as a deduction - along the lines of they agree to pay $100 for the pro bono work provided that you donate that money back to them - provided that you are entitled to claim the donation then the two would cancel out. If you are not entitled to claim the donation then you are better off not trying to assign a cash value to the work as if you did then you’d have income to declare and no deduction. Whichever way you work it out the best situation you can get for pro bono work is where you don’t have to pay any tax on it.
In Australia it would make a difference if it were an exchange of services rather than a donation of services with only one party registerd for GST since then you do need to work out the value of the services in order to pay the tax on that half of the exchange.