u/Andrija2567

When speaking about Lady Stoneheart being cut GRRM emphasised numerous times how much he regretted this change in the TV show:

>"She is an important character in the set of books," he notes. "(Keeping her character) is the change I most wish I could make in the (show)." - https://www.cnet.com/culture/entertainment/george-r-r-martin-game-of-thrones-drops-winds-of-winter-hint/

Note the date of the magazine, 2017. This was the year season 7 aired.

The only times when Aegon is mentioned by George are when mentioning all of the dozens of other characters that didn't make it to the show:

>Meanwhile Jhiqui, Aggo, Jhogo, Jeyne Poole, Dalla (and her child) and her sister Val, Princess Arianne Martell, Prince Quentyn Martell, Willas Tyrell, Ser Garlan the Gallant, Lord Wyman Manderly, the Shavepate, the Green Grace, Brown Ben Plumm, the Tattered Prince, Pretty Meris, Bloodbeard, Griff and Young Griff, and many more have never been part of the show, yet remain characters in the books. Several are viewpoint characters, and even those who are not may have significant roles in the story to come in THE WINDS OF WINTER and A DREAM OF SPRING - https://grrm.livejournal.com/465247.html

Why does he put emphasis on Lady Stoneheart being cut, but only gives passing mentions to a character many fans expect to play a far larger role in the story than her?

NG: Three more volumes of A Song of Ice and Fire wait to be
written. What shape do you expect them to take, and are their titles
finalized as yet?
GRRM: Yes, three more volumes remain. The series could almost be
considered as two linked trilogies, although I tend to think of it more
as one long story. The next book, A Dance With Dragons, will focus on
the return of Daenerys Targaryen to Westeros, and the conflicts that
creates.

https://www.infinityplus.co.uk/nonfiction/intgrrm.htm

Everything that will happen in Winds of Winter in the South was never meant to happen originally. Euron was never meant to be at Oldtown, but at Meereen, Faegon (Perkin Warbeck) vs Dany (Henry Tudor) would have been just another thorn for Dany in Westeros aside from her war with the Lannister regime.

But GRRM changed his plan, kept Dany in Meereen, married her to Hizdahr instead of a Greyjoy, breaking the Undying prophecy in the process, and had fAegon take the role of the original second act of the 1993 outline, that of a Targ claimant invading the realm just as the Lannisters won their war with the Starks while Euron was prevented from going to Dany because his captains forced him to invade the Reach, which was not a part of his plan.

Now the entire southern storyline has grown outta of his control, and he doesn't know how to resolve it. I honestly think he has no idea what he is doing with fAegon in the Stormlands, Euron in Oldtown, and Cersei in KL. Especially since George mentioned that he was struggling with several of Cersei's chapters in Winds. And who knows what the hell his original plan for Dorne was at the time Dany was meant to arrive first.

I think this is the reason why D&D took the ending for ADWD, Cersei's upcoming trial, Battle of Fire, Battle for Winterfell, and extended it to last until the very end of season 6, while Jaime and Euron arcs for that season consisted of material meant for AFFC, Kingsmoot, and Siege of Riverrun. It could be that GRRM really had nothing of note to tell D&D during their Santa Fe sitdown regarding this part of the story, so they used existing material to cover the Southern storylines while giving fAegon story to Dany.

[Spoilers MAIN] GRRM never emphasized Young Griff being cut from the show