I am answering my own question here.
In the meantime I digged more into this topic and I got an answer from one of the btrfs developers. He pointed me to a new function called ‘raid stripe tree’ which was introduced with kernel 6.7.
The commit says:
Introduce the RAID stripe tree, a new tree for logical file extent mapping where the physical mapping may not match on multiple devices. This is now used in zoned mode to implement RAID0/RAID1* profiles, but can be used in non-zoned mode as well. The support for RAID56 is in development and will eventually fix the problems with the current implementation. This is a backward incompatible feature and has to be enabled at mkfs time
Newer kernels did not receive any update to ‘raid stripe tree’. Which means that there is still no progress with regard to RAID56. But at least there is more hope now.