You did a good job removing the Widows related partitions. I assume your Windows 10 was an EFI/GPT install, therefore you probably still have code left in the EFI partition (disk0s1).

To view the contents of this EFI partition you have to mount it. You can do so with the command shown below.

    diskutil mount /dev/disk0s1

Below is a what I have in my EFI partition. I do not have any EFI dependent operating systems installed. If you have any folders that are Microsoft related, you can delete them. For example, the folder `EFI/Microsoft`.

[![enter image description here][1]][1]


You can also look for the folder `EFI/BOOT`. The apple firmware will recognize the file `bootx64.efi` in this folder as the default name for removable operating systems. You can delete this folder.

When finished, unmount the EFI partition with the following command.

    diskutil unmount /dev/disk0s1




  [1]: https://i.sstatic.net/x56Ah.png