It’s fine if developers execute the test cases and/or use checklists before handing over the application to testers for testing. However, the benefits will be evident if the developers actually use these
I would suggest, provide as much support as you can; to the developers in any way possible.
There is no risk or loss. It is good in a way that QAs will get the better quality code. And in case if testers don’t find any bug since they are re-running the same test cases then they can plan ad-hoc testing and/or monkey testing or anything.
You will have more time to experiment and find new ways to test the application.
There is nothing that can go wrong with this approach. The only thing is that testing team might be able to find lesser defect as they will get clean code.
Generally, because of the delivery pressure on developers, they don’t get enough time to harness the benefits of these helping documents. But, developers should actually test the code thoroughly even for functional scenarios before handing over the code to testers for testing.
From my perspective, it doesn’t matter how many bugs testing team raise; the only thing that matters is how many bugs are leaked.