I guess it would be for wildlife and bird folks, but I have never shot wildlife or birds and have no interest at all outside my own pets on rare occasion and I can live without it for that.
Based on the thread, I'm 100% convinced that if you don't shoot birds, you don't need an R5. That's the main reason I've decided to get an R6, maybe. Based on the thread over there, that's all it's good for.
The R6 and R5 both share the same IBIS, Auto-focus and Eye tracking systems, so your comment doesn't really make sense to me. The big differences between the R5 and R6 are:
1 Sensor Size. The R6 has the smaller 20MP unit based on that in the EOS 1DIII, while the R5 has a new 45MP sensor. This distinction has two implications: the smaller pixel count means larger pixels in the R6, so according to the reports I have read it has about 0.5-1 EV improvement of DR over the R5. On the other hand, the 50% greater pixel count of the R5 makes is suitable for situations where significant cropping might be desirable, or for resolution of very fine detail such as landscapes or situations where very extremely large, very high quality prints are going to be generated - perhaps studio or fashion photography.
2. Video. The video capabilities of the R6 are impressive but they don't include 8k, which the R5 does. While perhaps a niche market currently, the trend is towards more and more video resolution, so this is maturing market.
3. File Size. Logically leads on from sensor size and video output. The smaller sensor of the R6 is more agile in saving and transmitting images, which is why it is in the EOS 1DIII, a camera favoured by sport and journalistic photographers. The fact that the R5 takes 8k video has demanded that its throughput of the significantly bigger files be higher. This results in the inclusion of the Express CF as well as the SD card in the R5, while the R6 has (for still photographers) the much more convenient and cheaper dual SD cards.
4. Weather Sealing. The R5 has enhanced weather sealing over the R6, so it is intended more for the rigors of professional shooters over enthusiasts who have a choice not to shoot in less than optimal conditions, less so a pro.
5. Cost. Of course, one of the biggest differences is price... The R6 is a great enthusiasts camera, or a backup unit for professionals who want the extra features of the R5.
In conclusion, both the R5 and R6 have similar capabilities in focusing and tracking, but the R6 is more of a photographer's camera and less a videographers, compared to the R5's 8k video capabilities.
Not that it matters, there wasn't much to shoot anyway. Except a couple of Egyptian geese. As I was kneeling down one of them became very curious and came way too close to fit into the frame. Which was lucky, shooting in crop mode and all... 
