Please be assured that new features in XKit Rewritten do not enable themselves. The only circumstance in which anything will enable itself is if we replace a feature's option with something else (e.g. moving an option from Tweaks to No Recommended, or splitting one option into two that when combined do the same thing as the old option).

Panorama is not a new feature, but it has been broken for around two years as a result of Tumblr's new three-column site layout. What's likely is that you enabled the feature before or during this time, and now that it's fixed, it's obeying your pre-existing configuration and "suddenly" activating as a result.

If you have any recent configuration backups, you should be able to see Panorama in the list of enabled features there to corroborate what I've stated.