Nick - There was no modification to the Receiver required for the 1896 magazine cut-off "update".

The "reverse operation" was achieved simply by removing the original style cut-off lever and replacing it with the newly engineered one. The new levers were a 'retro-fit',  made and likely sent-out to units in large numbers. The new cut-off lever could be put on model 1892 and model 1896 Krags, easily. (The difficulty had been in designing such a fix)!

This change could be done by unit 'armorers' without the need to send U.S. Krags back to the Armory, arsenal, or depot.

1890 U.S. infantry tactics & thinking, (and the criteria that lead to the adoption of the Krag-Jorgensen design), stressed using the Magazine Arm as a "single-shot", with the magazine contents held in "reserve".
If a situation called for 'rapid fire', orders were given for the unit to do so. The cut-off would be switched to the 'feed' position to facilitate Rapid Fire.

Officers and Sergeants had to maintain strict 'Fire-Control'. All Krag Cut-Offs had to work the same way. If  soldiers tried to 'single-load' cartridges, with their Krags feeding from the magazine, jamming would occur!

In the later versions, the bottom of the 'cut-off lever' was polished 'bright' (in the 'white'), so it could be seen at a glance if a man had his Krag in the 'rapid-fire mode'.

IMHO - It would be more peculiar if your model 1896 rifle still had the early (obsolete) cut-off lever in place.

My suspicion is that your model 1896 got updated with the later cut-off, possibly in the field, but, escaped extensive changs that happened to many Krags that occurred in the early 1900's and WW1 rebuilding/repairs.

That is all pretty cool! (You can always eventually locate an earlier cut-off and keep it with your Krag, as a 'conversation piece').