New To Me HybridSD S3/S4 Condition

This morning I saw something in the HSD that I don't understand.

Base line conditions.: Air temp ~48 deg F. I had entered S4, verified with an
"idle check," and easily finding/holding no arrows glide above 42 MPH. I
then stopped for ~2 min. to debark passenger. Put the car in park, but did
not turn off ICE -- I do this because I believe it "preserves" S4 over the stop.

Resumed trip, but had difficulty finding/holding no arrows glide. Then it
happened... Speed 47 MPH, 6 blue bars, roadway level/very slight down
grade, can't find glide. Scan Gauge shows: 990 RPM, IGN 5 -- or maybe
switching between 5 and 10 -- coolant temp 170 deg F. Mimic shows yellow
arrows, battery assisted glide. 99.9 MPG

The weird thing is this went on for over a mile with speed remaining at
47 MPH, and the six blue bars never changed. I was just agog, and going
over a bump in the road I lost it. I motored up a slight rise with no arrows
to/from the HV battery, and then went into a half mile long no arrows
glide/regen as the expressway transitioned onto surface roads. Usually I
arrive here with six blue bars. But today I had eight green bars.

Can anyone help me understand what was going on -- the really low RPMs
and IGN, (S3 perhaps?) the HV battery seemingly not discharging despite
the extended yellow arrow "assisted glide," and the final full-up HV battery?

Is it possible that the HV battery was being charged (MG1?) and discharged
(MG2?) at the same time with the net charge increasing but staying in the
sixth blue bar display range?

 

Hobbit,

What is a "battery recalibration event?" Did a quick Google search with no
results.

Is it a good thing? Just CPU/ECU housekeeping?

There was some regen as the highway transitioned on a slight down slope to
surface roads, regen roll-down from say 40 MPH to 10 MPH. I wouldn't call it
a lot. I see this every day and it contributes to the typical six blue bars at this
location.

I'm gonna have to get off my butt and program the HV SOC, amps, and voltage
XGauges into the SG. I suppose that readouts from the first, and one of the later
two would be helpful investigative tools in a case like this.