Personally, I would prefer that the package managers keep their own lockfiles with all their metadata. A CI process (using the package managers itself) can create the SBOM for every commit in a standardized environment. We get all the same benefits without losing anything (the package managers can keep their own formats and metadata and remove anything unneeded for the SBOM from it).
Second that. It is trivial to add SBOM generator to your pipeline - it is not trivial to make all kind of package managers to switch and each format is used for different audiences.
To understand what an impossible task this is, there is no need to think about different ecosystems (PyPI vs NPM vs Cargo vs ...). Even in the case of different Linux distributions, the package managers are so different that expecting them to support the same formats is a lost cause.
I do exactly that in my container build pipelines and it is great. And then CI uploads those SBOMs to Dependency Track.
Depending on the language, scanning just the container is not enough, you for sure want to scan the lockfiles for full dependency list before it is compiled/packed/minified and becomes invisible to trivy/syft.
You are building everything in CI from scratch so theoretically, it should be completely possible to not need to scan lockfiles and get all the data from their respective sources (OS, runtime, dynamic libs, static deps, codegen tools, build time deps, etc)
