Stream download data instead of preallocating it? (exFAT/NFS amazing difference)

[qd3v]

I'm using qbt for a year now, and very satisfied with it. But one thing just makes me crazy each time I download something bigger than 5Gb: preallocation.
Specs: SSD+exFAT, win10/big sur
As noted here waiting of preallocation of 80Gb file may take xN times more than downloading it (1Gbps internet). The additional pain is the fact that recording of 80gb done twice, and I really can't see any reason to do that, on SSD for sure.
The interesting fact I found: downloading torrent to NFS works just like I want it to work: it just start to download as soon as new torrent added, not raping remote hard drive, no preallocation, no disk overload, maximum speed from first second to the last block, and looks like regular (non-torrent) download.
Is there any configuration magic I missed (I doubt, I tested every one, inc. preallocation/sparse switch) to make downloading as smooth as on NFS? Or this is OSes/FS issue? I suspect that NFS just don't have this PA feature, and that cause it work so great. Would be fun if stupid solution as downloading to NFS volume located at localhost will fix this issue :)
Thanks!
P.S. found al lot of issues about how to preallocate, I'm looking for the opposite, to save time and my SSD :)
The similar problem had Steam client until about a year ago they fixed that (downloading 100Gb game was a nightmare)

[ben-ba]

It seems, that the preallocation is only used for newly added torrents. So you have to readd your torrent or did you try that already?
(Note: Furthermore sometimes it happened for me, that when the disk is nearly full, preallocation doesn't work.)