Thanks for pointing out that those allpasses hidden in the patchers in the middle of the FDN tank.
I wonder how much the sound will suffer if we just use static allpasses in the reverb tank, compensating for that by using a six-line FDN instead of a four-line FDN and by putting 10 static allpasses in series before the main FDN tank.
Time for me to get my own Axoloti and find out for myself.