If you take an existing simple product and you only make a small tweak to its design, in a way that doesn’t impact manufacturing methods, there is no need for a DFM review.
In other cases, you need to confirm that your design can be made in a way that allows you to reach your objectives (budget, quality, timelines, …).
Read more about this on https://www.sofeast.com/product-engineering/dfm-review-asia.