There is a precendent for this concern over Rodinal batches. Here in Australia, because of low turnover and the long shelf life, it appears that Rodinal was imported by Agfa Australia at long intervals. My first bottle of Rodinal in the early 1970s was quite dark. Some years later, I bought a bottle that was fairly pale. Being a cynic, I cursed the manufacturers for meddling with the formula, but it still worked. I have since read that many customers here and in New Zealand were also disturbed by this, but as far as I know there really was no difference.
Does anyone know if the formula did change in the last 50 years?
Turnover here is still low. There was plenty of Rodinal at Vanbar North Melbourne last time I looked.