Nube,
You are comparing the same bullet to the same bullet, so there shouldn't be much difference, even though, occasionally, you run into a problem where the tooling for a particular lot of bullets did vary from the norm. But that is unlikely to be the problem here.
Nor is the problem the CIP specification vs. SAAMI. For cartridge overall length (COL) they are within two-tenths of a thousandth of and inch of one another after you make the metric conversions (divide any of
CIP's millimeter numbers by 25.4; it's an exact conversion factor by definition and with no unaccounted for digits afterward).
That said, I suggest you redo the measurements. I have noticed repeatedly with my match AR that the comparator insert is loose enough that the bullet hangs up on the way into the throat giving me a short measurement similar to what you are getting. The way to check this is simple. After you get the bullet comparator number, remove the adapter, zero the caliper, then make a COL measurement from the base to the tip of the bullet. Hornady recommends a COL of 2.25" for this bullet. If you get a result shorter than that, unless your chamber is defective (also unlikely) something is going wrong with the measurement as happens to me.
What I had to do to get the measurement right took two steps. One is I painted a bullet with Magic Marker and looked at where the chamber marked it. It was a line on the ogive below where a comparator contacts it. If the bullet is really all the way into contact with the throat, you should see rifling land's marks evenly spaced all around it. I had none.
When I figured out I was not getting contact, I wanted to know why? It turns out the gauge case being loose in the chamber plus the bullet being loose in the gauge adapter case is a combination that allows the bullet to tip too much and sit too far off-center to seat cleanly. It catches on the step at the end of the chamber's neck space.
To avoid that, set the gauge in the barrel and seat it as before. Pull it out. Using your caliper and an example of the Fiocchi load, set the rod in the gauge forward until you have the same COL in your gauge the Fiocchi does. Now hold the gun muzzle-up with your weak hand and slowly move the gauge in while you wiggle it around until you feel it slip in past the sticking point (it stops, but then goes in deeper). Then hold the gauge in place as you lay it down and then loosen the rod again and gently press the bullet in the rest of the way. I've gotten close to 1/4 inch more COL doing that with some bullets. Now you should see the rifling marks on your test bullet, too. Now you have a good measurement.