Dear Shri Sidharth Srivastav,
So far as the company law is concerned, you are correct in your obsertvation. But, with respect to the transmission of shares the question of PAN comes in the context of taxation laws due to transfer of wealth of the deceased and proper accounting for that. The need of PAN Card for NRIs, OCI or PIOs can arise only when they have taxable income in India. But, here it is a case of transmission of shares in the name of wife of the deceased, not in the name of NRIs/OCIs/PIOs, themselves. Form 60 in lieu of PAN is accepted from those who are not liable to file tax in India as they either have no income or their income is below the allowed tax free threshold. So, it is merely a formality to fulfill the requirement of taxation laws. But, where the NRIs/OCIs/PIOs don't possess the PAN Card due to having no taxation liability in India, they can fill in the Form 60 in liew of PAN Card.
But, there is no ban for the NRIs/OCIs/PIOs to apply for a PAN Card, as having a PAN Card does not necessarily need to file an ITR, if no income is there. But, PAN Card, if got can help such NRIs/OCIs/PIOs even for any further finance/ wealth related transactions or opening of Bank accountys in future also.