That's interesting, could you tell me more? Like which side and port (front/back) was throttling, which side and port was not? Were you using a power supply to charge or was the mbp connected to a display? Did it only throttle during charging or also during while fully charged? Thanks!
According to a response elsewhere on this thread, it's not an unknown problem and there are links to more specific answers than I care to write. But to answer your question, it throttled with either left-side thunderbolt ports, with nothing else plugged into the machine using the Apple-supplied charger. I cannot remember if this issue stopped when the device battery was at 100%.