But, wait for it... is not this some form of featuritis?
Or is the forensic field an exception to featuritis ?
Not at all, featuritis is another thing.
I dream about having n vertical tools that are excellent in providing exactly what is expected by them.
Clonedisk (that if I recall correctly made me start the featuritis conversation with you at the time) should (in my perverted mind of course) clone disks (and of course make images of them and of volumes, etc.), the more possibilities you add to the tool related to copying/backing up/etc. , i.e. strictly related to the "institutional scopes" of the tool are all good and fine, they represent sorts of corollaries to the tool.
The moment you add something that goes outside these (of course unwritten) "institutional scopes" of the tool, that is featuritis, which as said is not in itself a bad thing, only it usually tends to complicate, sometimes beyond recovery, the usability of the tool, or its UI or both.
To give you an example for clonedisk (where the toggling of "advanced" menu greatly mitigates the overload ):
Can it make a sparse image?
No, still that would be something that is part of what one would want when imaging a disk or volume, it would be both a corollary and a feature.
Can it make a number of (BTW useful, but in very specific use cases only) Registry edits?
Yes, and that is (a mild form of) featuritis. 
Back to here (extents) is the scope of the tool provide the exact location of a file as LBA on the Physicaldrive (no matter on which filesystem and no matter if occupying a cluster or not)?
If yes, then having it work for $MFT embedded files on NTFS is a plus (corollary), as well as having it work on FAT12/16/32 (and exFAT).
And no, you cannot even get away with renaming it to - say - NTFSextents, as it doesn't find the extents for perfectly valid files on a NTFS filesystem.
 now, be honest, if you were not already extremely familiar with the offreg.dll, and had you not the source code of clonedisk handy, would you have actually thought of adding those registry editing capabilities to clonedisk?
Or would you have written a separate tool, to be used only in a PE environment or however offline from a booted "second instance" of the OS, calling it - let's say - "PERegMod" or "Offline_Reg_Mod"