It's possible that both companies are behind schedule on actually building out data centers (since they are relying on the same companies to actually build the things).
Another possibility is that they are finding the next level of increasing the context window didn't actually give much of an improvement in output quality.
it's unlikely they are "slowing down" because of safety concerns. If they were concerned about safety, they would have been creating a safety framework (legislative, infrastructure, or code framework) for keeping these things safe. They wouldn't have suddenly started slowing down, that makes no sense. It dioes nothing to mske current models safer (and Sam Altman and Elon Musk definitely wouldn't call for a slowdown).