Bitbucket Pipelines feels like an unfinished beta of a CI system. It has plenty of features that even work, but they can't be composed. Parallel can't be used in sequences, or vice versa. Deployment steps can't be used in tag pipelines. Child pipelines can't have deployment steps, nor can the parent pipeline steps that call them be deployment steps.

Worst of all, the validator doesn't check for these restrictions. It will tell you that the pipeline is valid and then when you try to run it you'll get an error message. Sometimes only when it reaches the step with the error. Sometimes only after you merge, because that step only runs on the integration branch!

Do not use Bitbucket if you can avoid it.