I'm not sure it's a rushed job. After all Microsoft send one of their teams to help with the port. It also doesn't really mater how bad the performance is in the 100 players lobby or during the drop. The poor Jaguar CPU is probably overburdened with 100 players jumping around, shooting etc. That said, drops below 20 during gameplay are a big problem.
My personal impression is that PC perfromance improved over time. I, of course, still have drops but even the 100 player lobby tends to run close to 60 fps for me now on the testserver (tried it ~2 weeks ago, 1440p maxed settings), while there was constant stutter the first time I saw the game running on a similar system at a lower resolution. Pubg will probably never run locked 30 on xbox, but I'm optimistic it will improve over time.