On-Mark, hoss, others.
Thank you for details and experience. This is not simply approved for use, but the conditions and nuances.
As noted, depending on the ac and use, the chargers do not work that well, and there have been studies, where the chargers do not charge very well and do reduce battery life. As with many things, lab studies and ac certs do not translate to reality, but in real use, with the longer term studies, the issues have come to light.
One should also note the very specifics of the approval. I noted before, there are approvals for use on the flight deck, but dont stop there. That is not blanket approval for charging on the flight deck, nor charging while in use. Several airline cert do say approved for use, but are not approved for charging while in use, nor approved for charging on the flightdeck.
The use of these electronic devices is fairly new, and now that longer term information is available, one can see how the rules and regs are developing accordingly.