What I have been seeing is that there will be a mild refresh of the S550 for MY2021 and MY2022. The hybrids will be produced at Flat Rock with an expansion of those facilities. The nearby stamping plant might be producing various components.
Not sure what the confusion is, the s650 is a 2023MY.
Ford announced the would delayed the s650 by one year. Which gives them a extra year to produce the current mustang line up (350 & 500 too) along with an electric torque assist (ie: hybrid) version... for the next few years before jumping (rushing) into the s650.
You won't charge the hybrid mustang, it electric power will be used on acceleration and charge while driving, or braking (perhaps).
I'll easily take an RS engine in a Mustang PP2 w/electric TQ acceleration.... (& so will most buyers.... that is, if you want performance and not just nostalgic for sound.)