I did a lot of research on binary serialization at the University of Oxford. One of the papers I published is a comprehensive review of existing JSON-compatible

I did a lot of research on binary serialization at the University of Oxford. One of the papers I published is a comprehensive review of existing JSON-compatible serialization formats (https://arxiv.org/abs/2201.02089 https://arxiv.org/abs/2201.02089). It touches on Protocol Buffers (and >10 other formats) and I'm analyzing the resulting hexadecimals close to how the OP is doing. I also published a space-efficiency benchmark of those same formats (https://arxiv.org/abs/2201.03051 https://arxiv.org/abs/2201.03051) and ended up creating https://jsonbinpack.sourcemeta.com https://jsonbinpack.sourcemeta.com as a proposed technology that does binary serialization of JSON using JSON Schema.