I'm just stating that the real question about how good this will be or not will be what happens in practice. If not enough employees are volunteering for this, then entire program could end in failure. Will there be pressure to make this work from upper management?

The opt-in nature of this from existing employees is what makes this suspect. The question is will Walmart use their current employment relationship with these people to try and coerce them into opting in. Hiring outside help from people that Walmart has no previous relationship with doesn't raise such questions.

Walmart also doesn't have a great public image, so people are more likely to go over their actions with a fine-toothed comb.