It is not about commonality of same Author, it is about "level" in which the driver is "hooked".
Try Total Mounter (definitely different Authors) if you want to avoid (why) the Arsenal thingy:
Unrelated to your issue, but just FYI, the "format" command in windows is a "strange beast".
I take for granted that you are more familiar with DOS and/or Linux behaviour.
In Windows NT when you format a volume (inside a "real" disk) the FORMAT command will access the MBR and - if needed - change the partition ID of the corresponding entry in the partition table.
As well, the "generic" Windows system will change (silently) a disk signature if it is empty 00000000 or if it duplicated at the time of mounting accessing the disk (real or virtual).
IMDISK treats a volume as if it was a "superfloppy", i.e. with it beginning on "sector LBA 0", this is not a limitation, it is by design, and if you try using on IMDISK Format. in this case. treats the volume as a superfloppy (and thus sets sectors before 0), possibly avoiding to attempt reading or writing to the MBR partition table (or corresponding GPT structure)
DISM may well *need* to "identify" the volume (on a disk) by a number of parameters that reside outside the volume itself, among them, as said, the Disk Signature, the offset to the beginning of the volume or equivalent data from a GPT disk, and to do this may well access areas that simply do not exist in a mounted IMDISK volume (which is also BTW "transparent" to mountvol command):
And - still just for your interest - Ken Kato's VDK driver is "half-way" in the sense that it is NOT accessible from Disk Manager BUT mounted volumes are within the Mount Manager reach (and listed in mountvol):
Also, as Olof said:
If you prefer , while there is no doubt that you experienced an issue when using DISM on a IMDISK mounted volume, you were IMHO a tadbit too fast to call it a "possible bug in IMDISK", it is more likely that you are using a tool outside it's usage paradigm.