Creators in JPD most of the time will also need to access Jira Software Projects, since Product Owners work on Discovery but also on the Delivery managed at Jira Software
As JPD uses Jira Team-Managed engine, most of the features of JPD can be achieved using a Team-managed project, what leads to not subscribing to JPD.
Despite some added features in JPD compared to a Jira Team-Managed project, licensing a user in JPD for US$ 10.00 and having to license such user also at Jira Software for US$ 7.75 (Standard) means licensing the user twice for the Jira Core engine.
Like a Jira Software licensed user (US$ 7.75) is able to use also Jira Work Management (US$ 5.00) Projects for free, a JPD licensed creator (US$ 10.00) should be able to use a Jira Software Project (US$ 7.75) for free.
Makes sense?