Two things are happening there, I think:
1. Berry favours a union back-style low tackle position around the knees which takes about 0.5 of a second longer to get the ball carrier to ground, or at least makes it look like the carrier is getting through when he isn't. DWZ seems to have not yet worked this out, and cramps in because he thinks Berry's missing his man. This enables a late offload from the tackled player into the gap that DWZ vacates. If DWZ just held his line, the tackled player wouldn't be able to make that offload - not outside anyway.
2. DWZ loves an intercept. The problem is that for every one he makes at the moment, three offloads are getting past him.
Also in the second half he stayed wide and Berry missed and try scored, that’s why I was thinking of giving Pompey a go on the right, shore up the tackling and give DWZ confidence to stay wide