Welcome! Your English is fine!
I've never noticed a specific example of what you're describing in my collection, although one may exist. But the observation that yours occurs at specific frequencies leads me to speculate that what you're hearing is the natural variation that can occur in every guitar that is built. Taylor does a very good job of achieving consistency from guitar to guitar in any particular line (e.g., the 816's); but sometimes one comes out a little better-sounding -- or worse-sounding -- than the norm. That characteristic could be a result of natural variation in materials, a periodic (and likely, inadvertent) deviation in construction technique, or just an oddity that has no obvious explanation. In the end, though, it sounds like your 816 may be less responsive to some frequencies (i.e., low F, F#, G, G#, and A) than the average 816.
Unfortunately, if my theory is correct, this would mean that your luthier is also correct when he says that probably nothing other than time will improve the condition. Playing the guitar, thereby causing it to resonate, will help it to "open up" -- in other words, resonate better -- which might loosen up the 'tightness' in this observed frequency range. Good luck!