I completely agree with you (surprisingly). That's why I find out of the box efficiency comparisons completely dumb. Efficiency comparisons should be done at equal wattage,, in which case sure, the 7950x is more efficient (only in mt workloads) than the 13900k, but not by much. Best case scenario is 19% in vray, but usually it's around 10-15% in most workloads. On the other hand the 13900k is much more efficient in mixed workloads. Gaming is the only task where the 13900k stinks, but frankly so does the normal 7950x.
Out of the box efficiency is relevant for most people, as most people don't tweak settings much, if at all.