Okay, I finally had a bit more time to play with this, and here is what I have discovered:
It appears that, when note durations overlap from voice to voice, Dorico gets confused. Consider this example I’ve created:
As you can see, Dorico comprehends the harmonics just fine (I used diamond noteheads, but circle symbols work just as well), but I also had to notate the framing G chord as an 8th note rather than a dotted quarter note. Any attempt to extend the duration of that framing chord results in Dorico not understanding the B harmonic in the chords it overlaps (i.e. if you make it into a quarter note, you lose the B in the very next chord only, and a dotted quarter wipes out both Bs).
I’m guessing that Dorico has decided that the figure is unplayable if you try to literally hold the G chord as written…? I have no idea, actually, but this is definitely a bug that should be addressed. It is quite common for this type of thing to happen in piano music without incident. Seeing as how Albeniz was a virtuoso pianist whose works are often transcribed for guitar, it would stand to reason that someone transcribing one of his works might wish to follow a similar convention when notating guitar music.