I like this notation very much. I also found it first in Corigliano’s music. It has to be said that Corigliano’s handling of tuplet notation is particularly good and is comprised of an impressive arsenal of choices, all of them always used intelligently for maximum legibility. He we will use ordinary triplet notation, ratio-based number display, notehead based display such as above, and even “approximate” tuplets in unmeasured segments such as “ca. half-note tied to dotted half-note” (but with noteheads, of course). He seems to always make the best choice for any player to apprehend the correct performance of a tuplet quickly.
Nevertheless, although I am not a programmer, I know that Dorico tends to go for notation that is based on general principles; so even though such notation may not be difficult to implement for simple bracketed values (such as quarter-notes or dotted eighths), it would be far more complex to do when dealing with a 16th note tuplet starting on the last 16th of beat 2 and covering nine 16th notes for example. What is Dorico supposed to choose here? perhaps a 16th tied to a quarter; but what if we change the passage to an asymmetrical meter? Could we then make Dorico smart enough to present an array of noteheads suitable for clear reading. It sounds like a mess of problems unless the method was only used for simple values, which is what Corigliano tends to do (and sparingly). But still, I have to say that I have always found this notation to be pretty sweet. When a pianist in an orchestra sees a bar of 5/8 starting with an 8th note rest followed by a bunch of notes bracketed under a half-note, you don’t even have to ask yourself any question on how to perform the passage, even at first sight.