20230127
Mine (16" base model) was purchased in Nov/2021 and was almost never used on battery - now the cycle count is 29, while the capacity has been 93% for some 2-3 months.
Being alarmed by the very fast capacity decrease but NOT wanting to use AnDante as it's listed as a separate, running app making avoiding accidentally switching to & killing it hard, I decided almost 2 months ago, after an absolutely clean install of Ventura (I completely formatted the SSD befre install) that I really try to find out how Apple's Optimized Charging works.
I found out that even if I explicitly disable network access ("Never") and explicitly kill all apps (Skype, Slack, Mail, Safari, Xcode, terminal windows etc.) before closing the lid, if I do disonnect the power during sleep (which can take 16-18 hours a day as it's a home computer staying at home) and only reconnect it when I do use the MBP, Optimized Charging NEVER starts to be enabled. And the same stands for completely shutting down the machine instead of just sleeping: the charging level will always stay at 100%
Then, I found out that if I do keep it on the charger all the time, even when it sleeps, Optimized Charging does really "kick in" after 2-3 days. I've been keeping my MBP for exactly a month, since 29/Dec. There were only two distruptions during this - I don't know why they happened. On 11/Jan: I didn't open the MBP at all; the next morning was back at 100%, Onkly returned to 80% mode in the 13/Jan evening. And another unexplainable disruption also happened the next day: on the 14/Jan night, it was again at 100, from which started going back to 80% on the 16/Jan evening. It was on charger ALL the time.
That is, it was in the 80% mode between 29/Dec and 11/Jan and after 16/Jan. I really don't know why it "oscillated" between the two modes between 11/Jan and 16/Jan - I changed absolutely nothing during that period (did NOT restart / shut down the machine or operated on battery at all).
I also found out that you should NOT power down entirely as, then, it wiLL charge to 100% mode even if constantly on charger! just make it sleep.
That is,
1, do NOT shut down, only sleep!
2, ALWAYS keep it on charger!
BTW, I have two company-assigned 14" 10 core models (16/512). I don't keep them on the charger all the time, unlike with my home 16". I came up with the same conclusion with them: even if you don't use them on battery, just let them sleep, if the charger-less time exceeds the on-charger time on average, the 100% mode will be used. If however they're more on charger than without, they'll likely to resume 80% mode.