Not a Hummingbird expert by any means. The torrefied top (baked top) is an aging process, supposedly ages 10 years (at least that is my understanding). Compared to a standard vintage there are more differences than just the baked top, which adds to the sound - i.e. hide glue, the scalloped braces are more aggressive, it also uses bone for the nut, saddle and pins while the standard is tusq, the finish is thinner also, which again supposedly adds to the sound differences.
The new J45 vintage I believe is Adirondack right? I know of one selling at the Martin forum - 2019 Adi baked top and all the vintages goodies for $3K.