Unrecognized filesystem error when mounting system.img.ext4 with ImDisk Toolkit

I have an Android firmware file, which consists of raw partitions that can be flashed to a device. I was able to extract boot.img (needed for the device to boot) and system.img.ext4, which is an image of the device's /system partition, which is (typically) in ext4 format (the extension would seem to indicate so). I also have Ext2Fsd installed. When mounting this file with ImDisk TK, Windows complains that it doesn't have a recognized filesystem. I have tried manually assigning a letter with Ext2Fsd, but same error when I try to access it. I have also tried renaming the file to system.img before mounting, same error. I simply need to extract some files so that I can perform some operations. This is probably a task better suited to Linux, but I would rather use Windows. I was able to do this with another system.img from another firmware file (for an LG device) and it worked. The firmware file I'm using right now is from a Galaxy Note 4 running 6.x Marshmallow. What gives?

Finally, you found the ImDisk subforum...

 

Even if there are bugs, it is indeed possible to use ext2fsd.
Have you tried the command line?
imdisk -a -f system.img.ext4

Don't kid yourself, I never "found" anything, I always knew where it was since I joined the forum. I already stated in another thread why I'm not keen on posting here. I'll get around to trying your suggestion, although I'm pretty sure it won't work.

G:\Android>imdisk -a -f system.img.ext4
Creating device...
Created device 0: No mountpoint -> system.img.ext4
Done.