I'm wonder about softparticle

I’m not good at English. Maybe there are some error grammer in my content, please forgive me.
I watched this tutorial https://www.youtube.com/watch?v=oQzht2dE294&lc=UgwSy1BJ14MJQ1Gwft94AaABAg
but my particle doesn’t preform like the demonstration in video .

I’m worried that I ask too many questions ,and than I probably make the author of the tutorial feel annoyed, so I come here .

I collected so many informations on net and unity documentation, this effect of soft particle absolutely needs something like a depth texture.

So I confuse about this tutorial , it seems like work in “forward” , and it can performance with only shader , no enble depthtexturemode.Depth , but according to these informations I collected , it could not be .

I have ASE editor , and Renderring path is “Forward” , unity version is 2022.3.24f1.
I used Depth Fade node so many times, but it worked not like the tutorial I have watched.
It performs whole quad become transparent , not the edge between quad and other object become transparent graduately.
Is there other setting I did not notice?