It's usually easier for a technical "tech lead" to pick up project management than for a project manager to pick up "tech lead" (deep technical) skills, but exceptions exist.
The tech lead should have better business understanding than "currently needed" and ideally be supported by a domain expert (business analyst, product owner).
A project manager may support the tech lead to ensure the project's output ships.
This matches my experience - I was intentional about not saying that a project manager was important - just that project management (the practice) is important.