Correct, the horn only 'feels' them as a homogeneous oblong air mass lump until its BW between the two exceed ~1/3 WL of their acoustic centers, so are high enough in BW that at most, a minor amount of damping will quell them.
Correct, as indicated by my example. I doubt it's worth the effort for a HIFI/HT app, what with all the docs already done for the single driver design, so was basically just providing another 'piece' of a TH's design 'puzzle' for those few folks wanting to scratch design/build their own multiple driver TH.
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.