Can't remember the VAX page size, but it doesn't matter (see my other comments) because Unix of that era didn't have a rodata section. There was a single data section (eventually a.out separated data and bs , but data was still writable) that obviously couldn't have been read-only.

Rodata sections are a modern idea, the a.out binary format never had it. A.out explicitly documents the data section as writable. Rodata came with ELF.