Engine rules were simple to follow to this day - now even published official energy diagram is giving false information indicating some teams will brake the engine rules if charging up the battery via ICE. It's not allowed by published rules.
Edit
By Discussing with AI this really looks like that only way to charge battery is via MGU-K by terrible excuses and politics. By a car engineer point of view this looks like driver is trying to brake ICE and MGU-K by putting braking pressure under full throttle on same time on straights. (and even on tight curves according to some A. Newey)
What is going on at Formula 1 really....We may have a good laughs on next season. Even first tests are Top Secret because they know this is going to be a scandal but can't prevent it anymore.