You're right on one count; we should probably not follow up on the dragon ogres personally next turn regardless. We also shouldn't follow it right now, just report to the Expedition when we get back and let their collective prowess take on the problem. Here's why.
Let's say that we have an entire dragon ogre clan up in the mountains. It's functionally impossible to hide a slowly marching army of a hundred thousand from any group with even casual awareness of their surroundings, let alone one who has the kind of view that mountain peaks provide, so we cannot effectively hide the Expedition's existence from them. We also cannot take them out personally, because Mathilde doesn't have that kind of firepower.
So, if we ignore them for now and report their existence upon our return, what happens is that the War Council makes counter-dragon ogre contingency plans. These plans are probably something like "hope they don't attack, and if they do, swarm them with demigryph knights and any artillery we can rapidly bring to bear", because the War Council isn't interested in taking unnecessary losses fighting someone who isn't their objective, so they're not going to authorize an assault in force against the dragon ogres unless they're clearly aggressively hostile. Likewise there's no reason to not plan on hitting any attacking dragon ogres with all force we can muster to minimize losses. To make sure that they can actually make use of these plans if shit should hit the fan, they order all their scouts to keep an eye out for dragon ogres in the whole general direction that they think there might be dragon ogres in.
In contrast, if we follow this dragon ogre right now and successfully maintain stealth long enough to track it to its clan (no guarantee) and then escape unnoticed to report (also no guarantee), the War Council makes the exact same contingency plans except that they know exactly where the enemy is based so they allocate more scouts in that direction as a superior early warning system.
I don't think the relative benefit of the second case is worth the risk of Mathilde being noticed by the dragon ogre and then attacked/ambushed/generally squished, or worse, noticed by its whole clan and then same. Likewise, the benefit of Mathilde scouting for them personally again in future turns only moves us to the second case instead of providing any greater return, so it won't become worthwhile at any point in the future.
The only time we'd need to know exactly where this dragon ogre or group of dragon ogres live is if we're trying to lead a killteam after them, and I don't see that such a team exists or is likely to exist in the near future.