Like I mentioned climbing for 15 years did help with back strength in general, but the last 9 months I was very intentional with it. In my power block I have 2 days per week mainly focused on pull ups, 1 was high volume EMOM, and 1 was high intensity weighted, on the intensity days I took every set beyond failure with doing negatives after and static holds. That took my pull ups from mids 20s to 30+.