I'll be tolerant to an extent of the odd issue on a £400 phone (less if you include the freebies on ordering) but this would be unacceptable on a flagship.
Let's see how they handle it. I'm really hoping it's just software and be patched out. If it's hardware I might be slightly more annoyed.
That's the issue though, there's always something, sure the same can be said about other flagships but Google have been releasing phones with issues for a while now. Hoping the Quality Control improves in time for the Pixel 4 release. Hopefully like you say it's more of a software than hardware issue but relating to charging, could very well be hardware.