I suppose it comes to dealing with being close to the limit though. For most people that might be fine, for me it isn’t.
Also let’s be clear, most people aren’t shooting out to 300, I would say for those people the fox bullets are perfect. Out to 200y or if I’d been able to make the 100gr shoot I’d be happy to be using them and hopefully advocating their use. I’ve shot three deer with them. A muntjac at 140, no problem, it ran about 30y. A roe buck at, 180, again a short run but no problem. Another roe, 260y, ran on around 60y into cover, I though he stumbled, so I went straight over, he got up and buggered off. I came back in the morning with the dog and found him about 300y away, shot placement was good.
For most people I think they will be great, for me, they don’t work as well as the lead alternatives.