I think it's a bit of both; I do think Oda might have rushed the final chapters of Wano a bit because he wanted to get the Shanks cameo in before film Red.
I also suspect a few of the cutaway scenes from Egghead could have originally been planned for between arcs. In particular, it seems Oda saved Law vs. Blackbeard until after he revealed Pudding was abducted in the cover arc.
Beyond that though, he had Blackbeard and Shanks in two separate places, so I think he also spaced out the scenes just so readers get a better sense for the passage of time between the end of Wano / raid on Amazon Lily, and their current battles. I suppose the same can be said for Weevil and Marco. And Vivi with Morgans. Though I think all of those scenes also somewhat depended on information Oda revealed later on Egghead.
But back when Wano ended, I felt like everything was feeling a bit rushed - but everything clicked for me to an extent with chapter 1051 when Momo ascended to Shogun and chose not to open the borders. And the subsequent closing chapters on Wano made it even more clear. At the time I compared it to Fishman Island and I think that holds up; Oda deliberately left a lot unfinished on Wano.
It's more of a feature than a flaw because Wano demands to be revisited. The borders need to open. Kaido / Yamato's backstory remains incomplete because it will probably be picked back up again. And the history of the Kurozumi is likely no different. Oda's usually very good at addressing these themes - and they're deeply connected to the overall narrative arc of the series.
We already know Wano's history is tremendously important, that cycles of abuse and hatred are recurrent throughout the One Piece world - so it makes the most sense to address when Wano is revisited and the global war for revolution is really taking place.
All that also applies to Zoro and Ryuma's grave now knowing for sure (already speculated) that he is directly descended from Shimotsuki Ryuma through his grandmother.
The one scene I really wish we got to see was Chopper acknowledging his inability to heal the SMILE victims. I do like Oda's response and the resolution addressed in SBS, but I think seeing Chopper's emotions / response to being unable to help or heal some people with his current level of knowledge would have helped fuel his continued growth. Like a lighter version of the Nina Tucker scene from FMA. But I guess that could have taken away from the overall celebratory mood at the end of Wano.
As for he Carrot / Mink scene being rushed, I think that's even more conspicuous now. There were a lot of things at the end of Wano which many felt were dropped threads, but I think this SBS confirms much of my suspicion that those things are really setup for what's going to come later with Wano revisited. I guess this just hit home because I still vividly remember 12 years ago during Fishman Island posting long threads / theories about a secondary conflict on Fishman Island following Hody / VDD pointing to narrative elements Oda was setting up for the endgame as evidence (Sharley's prophecy, Noah, etc.). I also cited Hody's 'empty' lack of clear motivation - which, as it turns out, was the whole point of the arc.
So, when Momo ascended to Shogun, it just became clear - this current arc / saga wasn't even really about Luffy. Or at least, he wasn't at the center of it. The resolution is so much more satisfying when you center it on Momo's growth from helpless eight year old child who ran away from his homeland and traveled through time and across the sea to find allies and recruit them to join him in battle.
Oda pitted a helpless eight year old child, whose name ironically means invincible, against a pirate said to be the world's strongest creature. Powerscalers took Kaido's strength as a litmus test for Luffy's and have used the latter's victory to propel the main rubbery protagonist to the top of most tier lists, but in truth I think this misses the point; Kaido's purported strength directly juxtaposes Momo's perceived weakness. Luffy became a soldier sent into battle in support of general-shogun Momonosuke. The helpless child grew into an adult and became Shogun and that's why the big cathartic moment at the end of the battle coinciding with Kaido and Big Mom's downfall wasn't Luffy, Law, and Kid's triumph - but the moment in chapter 1051 when Momo declares himself Shogun. That's the scene which happens simultaneous to the eruption signaling the end of Kaido' reign.
Luffy, Law, and Kid played their parts and then faded into the background - while Momo was the one to claim victory.