Unfortunately this workflow is pretty fragile and it will not protect you from any of pip locking shortcomings.
It will basically work only in favorable cases where you have no ambiguous choice, no conflict (A depends on B==1.2.3, C depends on B==2.3.4), no reinstall to consider (git VS non git deps for instance), ... Really pip-tools is not that bad for now, until pip itself moves toward industry standards by default (lock file, deps resolution, reliable version checks, ..)
It will basically work only in favorable cases where you have no ambiguous choice, no conflict (A depends on B==1.2.3, C depends on B==2.3.4), no reinstall to consider (git VS non git deps for instance), ... Really pip-tools is not that bad for now, until pip itself moves toward industry standards by default (lock file, deps resolution, reliable version checks, ..)