The short of it, nope. I don't think it hurts it, and may even help.
Why?
Because first off, pentesting isn't just finding bugs. A full-scope pentest is finding bugs and using them to gain access, so leveraging them in the proper way. Whereas the whole point of a bug bounty is to just audit source code for something that the devs may have missed. Now imagine your running a site that has a bug bounty program, and you are getting lots of people posting bugs for their bounty. What are you going to worry about? The overall security of your site/app/network/operations. Logical next step would be to conduct a pentest to make sure that you've properly fixed said bugs, as well as to ensure the security of your network. This shouldn't be hurting pentesters any, and like I said it may in fact even contribute to even more tests being done.
Just how I see it, but you should ask some of the guys who work in the industry for their experience as well.
Cheers,
Daemon