Yes, I agree. Unfortunately, it's unrealistic to expect a huge company like P@H to change everything without legal developments to pressure them, especially in relation to an animal whose needs are relatively poorly known by the public. (Imagine the outcry if it were dogs!) It sounds as though things are getting better, and there is every reason to believe they will continue to do so, given the research and likely future regulations about rabbit housing.
A small charity such as the RWAF would be cutting off its nose to spite its face in refusing a reasonable-sized donation like this. The donor may not be fully up to their ethical standards, but at least the money doesn't come from the likes of a fur farm, and it is a good idea for them to keep dialogue open and on good terms with P@H to encourage further policy change.
Given that, as well as the unsold older stock, there will be animals dumped at P@H by former owners, it doesn't seem so bad that P@H put the animals up for adoption themselves rather than dumping them on an underfunded rescue. And I'm glad some of the adoption project money is going to animal charities, even if it's not quite as much as the compnay could probably afford. Maybe it's like those charity Christmas cards you get in department stores, where only 10p per pack actually goes to the charity.
I think the issue here really should be why P@H isn't donating more. They could probably spare the money.
The fund really isn't that big on a national scale. £10k would neuter, say 200 rabbits if the vet charges were lower than average (or perhaps rescues get lower prices).