Have you tried? The MS Media Creator creates a USB to install 64bit version of Windows 10, I don't believe you need a 64 bit system just to create the install media.
BTW, I found this.
When creating a bootable USB device, I am getting an error about bootsect
To make the USB drive bootable, you need to run a tool named bootsect.exe. In some cases, this tool needs to be downloaded from your Microsoft Store account. This may happen if you're trying to create a 64-bit bootable USB device from a 32-bit version of Windows. To download bootsect:
1. Login to your Microsoft Store account to view your purchase history.
2. Look for your Windows purchase.
3. Next to Windows, there is an Additional download options...