differing pathext behaviors

> cmd
Microsoft Windows [Version 10.0.20241.1005]
(c) 2020 Microsoft Corporation. All rights reserved.
C:\Users\oliver\AppData\Local\Temp>mkdir d1 d2
C:\Users\oliver\AppData\Local\Temp>echo @echo BAT >d1\a.bat
C:\Users\oliver\AppData\Local\Temp>echo @echo BAT >d2\a.bat
C:\Users\oliver\AppData\Local\Temp>echo print('PY') >d1\a.py
C:\Users\oliver\AppData\Local\Temp>echo print('PY') >d2\a.py
C:\Users\oliver\AppData\Local\Temp>set PATHEXT=.COM;.EXE;.BAT;.PY
C:\Users\oliver\AppData\Local\Temp>set PATH=d1;d2;%PATH%
C:\Users\oliver\AppData\Local\Temp>a
BAT
C:\Users\oliver\AppData\Local\Temp>set PATHEXT=.PY;.COM;.EXE;.BAT
C:\Users\oliver\AppData\Local\Temp>a
BAT
C:\Users\oliver\AppData\Local\Temp>cmd /c a
BAT
C:\Users\oliver\AppData\Local\Temp>pwsh -noprofile
[C:\Users\oliver\AppData\Local\Temp]
> echo $env:PATHEXT
.PY;.COM;.EXE;.BAT;.CPL
[C:\Users\oliver\AppData\Local\Temp]
> a
PY
[C:\Users\oliver\AppData\Local\Temp]
> $env:PATHEXT=".COM;.EXE;.BAT;.CPL;.PY"
[C:\Users\oliver\AppData\Local\Temp]
> a
BAT