I have used a few of those bluetooth headsets that are wireless stereo (TWS) ones and are charged by a case in which you insert them. I haven't used expensive ones, just rebranded chinese ones. All of them seem to get fully charged to 100% from 0% within 30 minutes. The case shuts off charging in 30 minutes and the phone displays 100% battery of the headsets.
So it seems the tiny 30 mAH or so lithium ion polymer batteries are charged at 2C charging current, which I doubt, even the highly advanced batteries of Tesla cars can't accept. How do these bluetooth batteries manage such high rate of charge?