Does anyone have an answer to this? Most POD accounts allow you to name multiple beneficiaries with your choice of percentages each beneficiary would receive, but some require equal shares period. It shouldn't matter to the financial institution and it really doesn't add any extra work for them.
I believe it would be to the FI's benefit to allow percentages. CD investors like their funds to be insured with the least number of financial institutions to invest in. They may want up to five beneficiaries so they could deposit more at the same institution and still be insured. But they may not want all 5 beneficiaries receiving equal shares, so they may limit how much they deposit in that FI or just skip them altogether.