this is confusing. I'd think that 'ms' is the time measured from the moment you submitted the share till you got response from the pool. and if so it wouldn't probably have to do anything with the miner version, but the network conditions. also obviously when the block time is short your ping better be fast.
Let's try another explanation.
If your computer is running basic addition and subtraction then it can solve a lot more math problems.
If my computer is running calculus then it solves less problems but they're more difficult.
Mining pools and mining software take this into calculating your hashrate and your rewards. Hashrate is not based only on how many/how fast you submit shares. It's also based on the difficulty of the shares you submit.
Look at, for example, Dwarfpool's ZEC pool. This is part of their configuration:
Main-Port (vardiff): 3333
Stratum-Port (dwarf=8,miner=256): 3334 for CPU
Stratum-Port (dwarf=128,miner=4096): 3335 for one videocard
Stratum-Port (dwarf=512,miner=16384): 3336 for rigs with 2-4 cards
Stratum-Port (dwarf=1024,miner=32768): 3337 for rigs with >=5 cards
What this means is that the difficulty is set higher on port 3337 than the other ports. 3334 is the lowest difficulty.
Port 3333 is regular varying difficulty. Most pools run this way. The difficulty varies.
Port 3334 is the lowest. Port 3337 is the highest... meaning the lowest difficulty setting on that port is a lot higher than 3334.