The /MediaArch x64 argument specifies that MCT downloads a 64-bit Windows 10 Enterprise edition – and in this case, v1909. If you need a 32-bit Windows version, change it to /MediaArch x86.
Some computers might be 64-bit capable but are limited by the amount of memory that can be installed. Windows 11/10 Home 64-bit supports up to 128 GB of RAM, while Windows 11/10 Pro, Education and ...