The problem with most full range drivers is the peak in between 2-4 khz, not only the extension above that, and I am not so sure that the Fertin is immune to such issues, one would need to see a frequency response curve.
How these peaks and dips affect the results is not so obvious.
Anyway, having speakers offering good high frequency performance is not a guarantee of "realism" (or "natural" sound). That would be too easy
The reverse may also be true - and you can confirm that with the many audiophiles going for vintage full range drivers that have limited upper frequency extension.