Change lead time includes the full lifecycle of the pull request from the first commit to deployment. Pull request cycle time excludes the last part of the lifecycle, time to deploy, and includes only the time from the first commit to pull request merge.
Despite being related, it makes the most sense to look at pull request cycle time and deployment metrics like change lead time separately. Slow time to deploy might mask the improvements you're making in the rest of your development process.
Using two separate metrics also ensures that missing lifecycle data does not skew the metrics. Pull request cycle time can be calculated for all pull requests, whereas change lead time is only calculated for pull requests that belong to applications that have deployments configured.