2. There is no spike protein anyone knows of which would have been used in this research
3. The PRRAR furin cleavage site is not one humans would have tried it is unlike any other known furin cleavage sites in coronaviruses
4. There are now many known related sarbecoviruses which have been found with furin cleavage sites
5. Furin cleavage sites have independently evolved in multiple different branches of coronaviruses, probably a dozen times that we know of now.
6. The furin cleavage site is short and can easily happen through recombination with another virus due to coinfection.
7. This is very likely what happened due to infection with the SARS-CoV-2 ancestor and an HKU9-like virus.
It is not particularly suspicious that the thing which we were worried about happening and causing a zoonotic spillover event is the thing which actually happened.
They were going to experiment with multiple backbones, experimenting with multiple variations of spikes, looking specifically to try novel types of furin cleavage sites.
There was no public reporting of what happened with this research. We don't know what they have because WIV database was taken offline. They claimed to have searched it, but what they claimed was the closest match in the database was not, in fact, as close as a sequence they had published. Given that demonstrable lie, there is no way to verify any claim about what sequences were or were not known and possibly involved in this research.
Furthermore the person who submitted the proposal was also the person who broke ethical standards to preemptively shut down all discussion of a human release.
That isn't to take away from the possibility of a natural spillover. The facts that you say about that are facts. But accidental release is also possible. And the lack of transparency from those who are most likely to have made the mistake heightens suspicions, it does not lessen them.