Defender exclusion doesn't work

Hi folks,

I'm working with Defender for Endpoint, managed through SCCM. I've attempted to set a folder exclusion for C:\test_folder\ via SCCM -> Antimalware Policies -> My Policy -> Exclusion Settings -> Excluded files and folders.

https://preview.redd.it/3tem7smpzblc1.png?width=1125&format=png&auto=webp&s=6ac1ac56a5b741503780d7f379a3ac46e82fd352

Everything appears correct; the excluded folder is visible in Windows settings and in the results of the Get-MpPreference command.

https://preview.redd.it/ertqhpglzblc1.png?width=1186&format=png&auto=webp&s=62659e1b0fa8d7ba97f55faeb65a8d22f4583d5a

https://preview.redd.it/lntd9dhozblc1.png?width=810&format=png&auto=webp&s=732c47172b41f2292dba712acb889a6f12e9f2b5

However, when I try to download the EICAR test file (Invoke-WebRequest "https://secure.eicar.org/eicar.com.txt" -OutFile test.txt), Defender immediately reacts by deleting it. I've successfully set several exclusions in the same manner before and they worked as expected, so I'm unsure if I've made a mistake or forgotten an additional step.

Could someone offer some guidance?