It was indeed changed recently and looking at the git timeline, it looks like it was done starting in v6.2.16.
I did not see any issue on my machine because in the mean time I added dedicated drives using one of these puppies and moved the data files out of my main partition.
Unfortunately, I cannot edit the original message!
So from 6.2.16 and up, it should look like:
...
## Default parameters for individual fdbserver processes
[fdbserver]
public_address = auto:$ID
listen_address = public
parentpid = $PID
command=...
datadir=...
logdir=...
knob_min_available_space_ratio=0.001
And again, it should only be done on a local development machine, NOT on production servers because it could impact how replication works!