Hi rossy syida,
Thanks for link.
Snack foods not my area of expertise but, TBH, I'm not sure why the dessicant/O2 absorber would be expected to have any particular effect on pH ?. AFAIK, pH and moisture (> water activity) are usually regarded as independent variables although their interactions are interpreted with respect to other food characteristics, eg PHF.
I daresay food ingredients such as buffering agents may also be involved in the linked article ? No sample compositions are mentioned unfortunately.
IMO it's also difficult to interpret the moisture/pH data since no replicates were used. The authors seem to believe the pH was essentially constant in all runs. Some of the moisture points listed look a little strange and might have been worth "repeating".