NRIs who became foreign citizens prior to 2002 didn't all lose the legal right to own immovable property in India. I'll have to check with what the pre-2002 legal status of bank account and bank lockers were for those who went from being NRIs to being foreign citizens, but for immovable property and even movable, titled property, it wasn't as grey as perceived by a lot of lay folk and even some others who could have known better but didn't.

Is it fair to say that your mother didn't get commonly perceived to be of an ethnic Indian origin? Indians giving a tougher time to perceived foreigners regardless of the law still continues, as with the hassles many a person from NE border states, Ladakh and Kashmir can attest to when having visited say the Taj Mahal and trying to use the Indian ticket pricing as resident Indians even within the past 12 months.

For NRIs and foreign citizen persons perceived to be of Indian ethnic origin, things in India have gotten easier indeed; but some of that is due to the mushrooming numbers of such people leading to Indians' increased exposure to how to handle such matters; and a lot of that is due to the OCI scheme even more than just to the PIO scheme.