How are they expecting us to have Max Rock fall and Lock-on at the same time?

The dynamax attack is tied to whatever the typing for your fast attack is, so how is this achievable according to this team recommendation?

My Regirock switches to Max Strike after changing its fast attack to Lock-On, so I’m a bit confused (I know Lock-On is the most recommended move since it offers faster charge, so I’d like to know how to achieve this).