I have seen other similar project using that vesting strategy, it doesn't guarantee a stable price, but at least give some breathing space to small investors.
Well if team doesn't have a vesting period but they believe the project, they won't sell. Still, it is a guarantee for investors that founders won't dump at day one. Doesn't have a big impact if they are trustworthy.
It's a touch subject to tackle. The team should obviously be able to sell come coins so that they can get paid for their hard work but obviously no one wants to see the price dumped.