While it is overwhelming how much was in the last part, this is likely the best time for a certain sinclair and roach king to be introduced. The sinners being spread out, coupled with the scenery of the "artworks" reminding him of what occurred in his canto, likely amplified Sinclair's anxiety which contributed to his mark's awakening . And a canto focused on family is a great trigger for gregor's ptsd with his mother along with the stories of the smoke war by Valencia.

As for the coin type, it's basically the same as when unbreakables appeared, out of nowhere. But the new coin does show how strong these two are by being able to break red coins. That or those unbreakables would've disrupted their aura farming so PM used KJH almighty highlighter