Nope
The benefit of concentric aka coaxial designs is to avoid that nasty dip around the cross over region when going off-axis.
With "planar" many myths have sprouted from incoherent technical speculation. For instance the moving pattern of a planar's membrane is literally chaotic in space, means phase correlation between parts of the membrane is just lost, aka "break up", but to the extreme (see DML speaker).. An electrostatic experiences positive feedback due to mirror charges ... many more.
Who is Gallo? Is there a place in tech for misleading sentiment? Is the majority right?
Not to tell, that all these examples didn't even deliver!
"Time accuracy" is achieved only today to some degree by digital, frequency dependent phase shifting--as an aftermath. This is the only way to possibly have some "time alignment" to speak of. (So that it can be measured reasonably, mind You.) Your examples only show unsuccessful attempts, story telling, no actual realisations.
So, with modern tools is was found that all the "time alignment" wasn't worth the effort in the first place--again not to forget that all the legacy effort never delivered anything! See
https://www.audiosciencereview.com/...g-klippel-andrew-jones-and-james-croft.11291/
Regarding slanted baffles see my post
=> #76 with an example.