Appreciate Mohan PB's effort in analysing most of the answers and sharing the comments. Valuable comments from Venugopal and many others!!
I still do stand by my opinion that it should not be "essential criterion" but should be a "good to have".
Let me give a hypothetical example to explain my thought process.
I understand the BB certification process consists of 2 steps:
Step 1. Passing an Examination to prove technical and conceptual Six Sigma knowledge
Step 2. Project to exhibit practical knowledge.
Most people, complete step 1 and are stuck looking for opportunities to complete Step 2. What can these people be called - If not "Certified BB" then may be "Trained BB"?
Consider two candidates A and B with following background profiles applying for a improvement Manager position in your company:
A - Trained BB (Step 1) - understands Six sigma concepts and techniques, questions existing processes and enthusiastic with a keen eye for process improvement opportunities. He has been a project manager for various technical projects - handled teams, interacted with management /customers , resolved conflicts, but has not been involved in Six Sigma projects.
B - Certified BB - Due to unavoidable circumstances, he had to move to the the Quality department in his company. He has completed certification and has completed projects to save and sustain his "Job". Now due to some reasons he has to change companies, but Six sigma is the field he has been working in most recently and is experienced certified in, so he has to apply for similar positions.
Now, my argument is based on the fact, that if project execution is "essential criterion" then Candidate A becomes ineligible and the company is left with no choice , but only candidate B. This is not favourable, because candidate A with some mentoring (learning gap) could have been a better option than B.
On the other hand, if project execution experience is a "good-to have" criterion, then the company would have had both candidates and can evaluate between them.
I am not suggesting that a newbie who has just academic knowledge on six sigma should be considered.
I am only suggesting that a experienced professional who understands and is experienced in project management/execution ( team building, conflict resolution, communication with management) and technically clear on six sigma methodology/concepts should not be left out from consideration, only due to the fact that he may not have executed six sigma projects.
If a company gets two candidates with similar skill set and same enthusiasm for improvement projects, then preference can definitely be given to the candidate with project experience, but it should not be made an eligibility/essential criterion.