This is what i get with you instructions:
Microsoft Windows [Version 10.0.22000.376]
(c) Microsoft Corporation. Alle Rechte vorbehalten.
C:\Users\Stasc>dir
Volume in Laufwerk C: hat keine Bezeichnung.
Volumeseriennummer: AE54-AEA9
Verzeichnis von C:\Users\Stasc
05.01.2022 18:19 <DIR> .
17.10.2021 14:03 <DIR> ..
03.01.2022 18:45 <DIR> .android
23.08.2021 11:14 <DIR> 3D Objects
17.10.2021 14:06 <DIR> Contacts
05.01.2022 22:43 <DIR> Desktop
23.11.2021 17:32 <DIR> Documents
21.12.2021 19:08 <DIR> Downloads
17.10.2021 14:06 <DIR> Favorites
17.10.2021 14:06 <DIR> Links
17.10.2021 14:06 <DIR> Music
20.10.2021 19:04 <DIR> OneDrive
17.10.2021 14:06 <DIR> Pictures
18.09.2021 16:27 <DIR> Roaming
17.10.2021 14:06 <DIR> Saved Games
17.10.2021 14:06 <DIR> Searches
28.09.2021 19:34 0 Sti_Trace.log
28.08.2021 13:31 <DIR> Tracing
06.12.2021 17:56 <DIR> Videos
1 Datei(en), 0 Bytes
18 Verzeichnis(se), 342.854.299.648 Bytes frei
C:\Users\Stasc>cd C:\Users\Stasc\Downloads\Poco F3\Rom\Fastboot
C:\Users\Stasc\Downloads\Poco F3\Rom\Fastboot>dir
Volume in Laufwerk C: hat keine Bezeichnung.
Volumeseriennummer: AE54-AEA9
Verzeichnis von C:\Users\Stasc\Downloads\Poco F3\Rom\Fastboot
05.01.2022 19:10 <DIR> .
04.01.2022 18:41 <DIR> ..
03.01.2022 18:32 <DIR> images
01.01.2008 00:00 2.322 linux_fastboot_first_install_with_data_format.sh
01.01.2008 00:00 2.024 linux_fastboot_update_rom.sh
01.01.2008 00:00 2.352 macos_fastboot_first_install_with_data_format.sh
01.01.2008 00:00 2.052 macos_fastboot_update_rom.sh
03.01.2022 18:32 <DIR> platform-tools-darwin
03.01.2022 18:32 <DIR> platform-tools-linux
04.01.2022 19:39 <DIR> platform-tools-windows
01.01.2008 00:00 2.395 windows_fastboot_first_install_with_data_format.bat
01.01.2008 00:00 2.111 windows_fastboot_update_rom.bat
01.01.2022 10:37 3.944.620.958 xiaomi.eu_multi_HMK40_POCOF3_21.12.30_v13-12-fastboot.zip
05.01.2022 19:10 3.897.462.712 xiaomi.eu_multi_HMK40_POCOF3_V13.0.2.0.SKHCNXM_v13-12-fastboot.zip
8 Datei(en), 7.842.096.926 Bytes
6 Verzeichnis(se), 342.853.799.936 Bytes frei
C:\Users\Stasc\Downloads\Poco F3\Rom\Fastboot>platform-tools-windows\fastboot getvar product product:alioth
< waiting for any device >
getvar

roduct FAILED (Status read failed (Too many links))
fastboot: usage: unknown command product:alioth
C:\Users\Stasc\Downloads\Poco F3\Rom\Fastboot>platform-tools-windows\fastboot getvar product product:alioth
getvar

roduct FAILED (Write to device failed (Too many links))
fastboot: usage: unknown command product:alioth
C:\Users\Stasc\Downloads\Poco F3\Rom\Fastboot>