I repeated the test by changing the strategy.
Shot another high contrast scene and produced both the version from the Raw conversion feature in the camera itself, so exactly the same shot.
Loading both the versions in Lightroom you can clearly see the histogram expanding on the sides for the AdobeRGB version, which means more contrast, which translates in less detail for shadows and highlights.
To mitigate what I wrote on the first post, you can actually set a softer settings for the highlight recovery when working with AdobeRGB and a step (or two) above setting for the sRGB version.
Anyway the first assumption is valid. AdobeRGB = less dynamic range.