Not if you use git submodules, which is how most people would end up using such a scheme in practice (and the handful of people that do this have ended up using submodules).
Go-style vendoring does dump everything into a directory but that has other downsides. I also question how effectively you can audit dependencies this way -- C developers don't have to do this unless there's a problem they're debugging, and at least for C it is maybe a tractible problem to audit your entire dependency graph for every release (of which there are relatively few).
Unfortunately IMHO the core issue is that making the packaging and shipping of libraries easy necessarily leads to an explosion of libraries with no mechanism to review them -- you cannot solve the latter without sacrificing the former. There were some attempts to crowd-source auditing as plugins for these package managers but none of them bore fruit AFAIK (there is cargo-audit but that only solves one part of the puzzle -- there really needs to be a way to mark packages as "probably trustworthy" and "really untrustworthy" based on ratings in a hard-to-gamify way).
Go-style vendoring does dump everything into a directory but that has other downsides. I also question how effectively you can audit dependencies this way -- C developers don't have to do this unless there's a problem they're debugging, and at least for C it is maybe a tractible problem to audit your entire dependency graph for every release (of which there are relatively few).
Unfortunately IMHO the core issue is that making the packaging and shipping of libraries easy necessarily leads to an explosion of libraries with no mechanism to review them -- you cannot solve the latter without sacrificing the former. There were some attempts to crowd-source auditing as plugins for these package managers but none of them bore fruit AFAIK (there is cargo-audit but that only solves one part of the puzzle -- there really needs to be a way to mark packages as "probably trustworthy" and "really untrustworthy" based on ratings in a hard-to-gamify way).