We've seen roaring moon ex utilize significant amounts of water energy just for rad greninja. This walking wake can slot well into this archetype and allows you to use a single prizer that hits harder than morpeko. 180 is still solid for a single prizer as you can still roaring moon ex them for 100 or 220 afterwards. However, the strength of morpeko is that it doesn't hinder powering up your roaring moon ex.
Radiant Ninja covered a much more significant role when devoted water energy: Knocking out 2 pokemon at once. That was something Roaring Moon ex could not do at all. Chaining together 2 1-prizers that only take 2 prizes cumulative is risky as heck in a dedicated Roaring Moon ex deck because you are leaving a lot of time for the opponent to just take some form of a 2-prize knockout from a bench snipe and fall behind the prize trade forever. Roaring Moon ex decks, including those now, play really aggro in staying ahead in the prize race.
In the same vein of a one-prizer attacking for OK damage numbers past the point where Greninja would be effective, it is much easier to include baby Roaring Moon for 2 Dark Energy instead of 2 Water + 1 Dark and at least 1 E-Switch needed.
Either way, decks that feature Roaring Moon ex have been on a decline in favor of Dino Box / Baby Roaring Moon focused builds.
Yeah Chip Richey and Azul GG were talking about (on their podcast) how post-rotation Ancient Box seems to be oriented towards two hit KOs using one-prizes, with maybe a Roaring Move OHKO to take the last two prizes in one fell swoop.
For context, this is a completely different deck than the one angooseburger is describing. These are decks featuring the regular Roaring Moon from Temporal Forces, and usually have one of two cores of Ancient pokemon
They tend to either run:
4 Roaring Moon
3-4 Koraidon
Some count of Flutter Mane, Slither Wing and/or Great Tusk
0 Roaring Moon ex
Or:
4 Roaring Moon
1-3 Roaring Moon ex
Some count of Flutter Mane and/or Great Tusk
The former uses Koraidon to hit middling numbers early and use Roaring Moon to hit stronger numbers, if not OHKO numbers, later in the game once you build it up. These Dino Box lists opt for consistently reaching two attachments for Koraidon, Slither Wing, Roaring Moon, and Great Tusk. They have absolutely no reason to run Walking Wake, and doing so would mean adding a third energy type and Energy Switch.
The latter uses Roaring Moon ex and Roaring Moon to keep whatever tempo of KOs they want, while only running Dark Energy and ensuring good use of Dark Patch. These lists have so far only included Energy Switch at this point to facilitate Radiant Greninja with Water Energy, which still fulfils the same function as it did in decks focusing on Roaring Moon ex. Though it needs 1 less attachment, Walking Wake would basically have to attack turn 1, or maybe turn 2, to not get completely outdone by Baby Roaring Moon. Since it would be attacking that early, it would be either attacking into a 1-prizer that Baby Ninja would handle a lot better in certain matchups, or a 2-prize basic that Roaring Moon ex chews out more efficiently and aggressively.
Long story short in all this: Walking Wake's 3-energy need is way too cumbersome to include in Dino Box, and rather outmatched by Radiant Greninja elsewhere. If it hit higher damage OR only had 2-energy requirement, it would be much more considerable.