But if that is really an improvement the sound or just changes it is up to debate.It’s different for the WM1ZM2 and WM1AM2, these support DSEE Ultimate over Bluetooth(encoded signal).
For compress low quality audio, its a big improvement, yes. But if you're listening to >=320kbps AAC its pretty much inaudible.
But even with low quality audio, its not like a day and night difference. I would never every recommend an WM1 Series DAP to anyone who wants to use it using LDAC (Sender). This tiny improvement that DSEE Ultiamte causes is a nice feature if you have the DAP anyway, but not a reason to get it.