Observe the above table. It did not exist for new claimants. The number of existing claimants is not yet zero.

The rates for DLA have never been significantly higher than PIP since the creation of PIP as a benefit. I have been following this, as I have been on DLA since before the introduction of PIP, migrating some three years after PIP came into existance.

If your father was getting significantly more than PIP, on DLA, either he was found to be not meeting the criteria for PIP, or he was getting some additional benefit, possibly help with health care costs.

https://www.gov.uk/government/statistics/dwp-benefits-statistics-august-2022/dwp-benefits-statistics-august-2022 - showing there were 1.2M claimants remaining in 2022.