The main difference is that in older pool software there was a hardcoded block reward of 3 sem. But now it reads block reward directly:
https://github.com/orogvany/semux-pool/commit/239a316e2bee337e5e293df88c5b70aeca6f8a4d#diff-c30456586563df8bc835517778fe7aaaR205-R208

So older pools can make wrong payouts after the block reward adjustment happened earlier today. Old pools can overpay some voters and thus won't have enough funds to pay for the rest.
So it's better to update pool software to the latest version for not having any issues with payouts.