Yep it leans out the AFR when coasting.

the wheels are moving your engine when you are engine braking. Not the other way around.

when you switch to neutral the engine needs to burn fuel to keep up idle rpms so it doesn't stall.

which it doesn't need to do if the wheels are moving the engine while it's in gear.

Hi, NO one has brought up clutching in at very high speed thinking the revs will come down and can engine idle down to a more legal speed WRONG
With rev match turned on , ,clutch in and car just goes straight into red light rev warning and it pings the rev counter .Then ya get lost in the gears and have to look at speedo to see what gear your in ,
blumin freaky when it happens 1st time . while you are "travlerlating " LOL travlerating is your off the speedo

Based on what you wrote here, I assume you started driving a manual this year.

Regardless of rev matching function, and regardless of speed, if you downshift into a lower gear while still high up in the revs and you let go off the clutch - you risk overreving the engine and doing permanent damage.
If you are just shifting in a gear and not releasing the clutch - nothing happens (with exception of potentially grinding synchro gears in the transmission).
If you are shifting in a gear with rev match turned on and again, not releasing the clutch - the ECU will try to match the revs, which it can't, because of the rev limiter and it will just hit it the limiter, nothing will happen unless you let go off the clutch.

Why and how you would "get lost in the gears" is unclear to me, but feel free to explain it.

:confused:
https://i.kym-cdn.com/entries/icons/...edtravolta.jpg