Crust is, simplifying a bit, just something that enables suspend to RAM on Allwinner platforms. From what I know you don't need anything like that on i.MX8MQ, since the SoC and PMIC will already take care of what's needed there by themselves.

Keep in mind that that "idle time" is actually "suspended time" - to handle things like incoming notifications over the Internet you still have to periodically wake up. Without suspend, PinePhone currently has a pretty similar idle power usage to Librem 5's. Once Librem 5 starts utilizing suspend to RAM, it should see a very similar improvement like the one you're linking to.

Crust runs in a RISC cpu inside the Allwinner chip, and it only works in that. I don't know if the NXP chip has a 'dedicated' core to manage the actual ARM cores, but all the work done in Crust won't be portable to the Librem, if it can be done, it'll have to be done from scratch