I can respond directly on why, perhaps, it would be a support program rather than an exemption. There are a couple of reasons.
There are some technical issues. For example, the delivery of natural gas and propane is slightly different from the delivery of gasoline and diesel, which is exempt. It's generally piped in directly and continuously. You may have a situation where it's not just the farm operations receiving the natural gas but also the house that's being fed the natural gas. It would be difficult to distinguish and take the fuel charge off the farm operation use versus the house use when it's a single meter. There's house heating, or they might have a barbecue hooked up to the natural gas, and that would be exempt from the fuel charge. So there are some technical issues.
There's also the issue of the price signal. At the very least, with the ex post relief, you're maintaining the price signal. It still presents an incentive for farmers to find more efficient, greener, lower GHG-emitting ways of engaging in their farm operations. The ultimate objective, really, is to have nobody pay this fuel charge. It's the change in behaviour via technology. Where farmers can't do this, well, they're getting the money back, so there is financial support for them.
Those are the two main reasons it's been chosen—