Its a recalibration of the IMA SoC (State of Charge) and of what the BCM "thinks" is should be. Shows on the dash SoC gauge as a rapid drop of SoC without a sustained assist to cause it. Followed by a forced charge.
You can make your own "faux recal" by parking the car & shutting it off, then disconnecting the 12v battery, then waiting like 5 minutes, then reconnecting it. The Soc reading will be really low for awhile but will ramp back up to normal after it's been driven awhile.
By definition a recal is automatic and unpredictable. Your procedure is a reset. Sometimes a helpful tool. The BCM can sometimes slip into the SoC doldrums for _days / weeks_ at a time and cause IMA Charge & Assist to fail to act "normally". A reset "refreshes" the BCM and will "fix" the "problem".
00-02 5 spds and without the updated MCM & BCM's are the most prone to this "problem". CVT's manage IMA load somewhat differently and rarely exhibit this behavior.
However, like you wrote the result is the same. And about 60 sec is the maximum time with the 12v disconnected that is required.
On my 37-mile, rolling-hill, mostly-highway commute:
SOC started around 55% down, then held at 70% down, then next thing I knew it
showed only 3 bars and stayed that way for probably 25 miles until end of trip.
I was - needless to say - avoiding "Assist" AMAP.
Coming home it was - again - showing only 3 bars of charge
for maybe 5 mins., then jumpted to 5 and kept coming back up,
After about 30 miles it was at 1-2 bars from full, and stayed that way.
Things that might have triggered this:
- car sat undriven for 48 hrs.
- some careless city driving prior to that left SOC down, maybe by 40%.
But in general, I've rarely parked the car with SOC down by more than 3 bars, sometimes around 30% but that's unusual.
While a recal can occur at any beginning SoC your 70% down (30% remaining) is a very low start. It wouldn't take much to "use" that amount of battery SoC in rolling hills.
So from your description I'd say no, you didn't expereince a recal. And their "normal". Its the frequency of occurance with traffic and terrain factored in that can indicate an IMA pack near the end of its service life.
I'm not sure if I experienced a recal or just very slow charging. I drove from NJ to Albany NY on the thruway (generally rolling hills, nothing too steep) and was in a hurry so I went kind of fast. My battery got down to 3 bars and stayed there for the entire trip (roughly 120 miles) despite the charge indicator lighting at 3-4 bars almost the whole way. The battery indicator stayed low through my street driving in Albany, the climb up the big hill to Grafton NY, and didn't charge again until I coasted the 15 miles down from Grafton to Troy. It filled up to 100% and didn't drop below 80% despite "normal driving" for the next few days.
whatever it was, it was pretty scary! I was very uncomfortable driving for 2 hours with such a low charge!
IMA SoC _will_ vary for many different reasons. Perhaps the #1 is more assist that charge. (you used it faster than it was replentished). And remember there are several battery "management" functions going on behind the scene in regard to extending their service life.
Give yourself the time to learn what is normal. And the "feel" for driving conditions that can contribute to something that appears to be abnormal. Then expect the ocasional unusual SoC indication. Should the unusual persist for more than a few days under "normal" driving conditions then the IMA reset is a common cure.