Actually the counting speed can be faster than 2MHz in WC8 hardware counter, if the pulses are short burst fast pulses. Since CPU must internally handle that counts, it limited continuously incoming pulses to 2MHz frequency. Single pulse can be as short as TTL gate can read, it should count correctly.
As to DS2423 chip being used in that mentioned, that is one wire. And it is being phased out by Maxim for last four years, Maxim support engineers told us other I2C version can only counts at 1Hz, or 1/8 HZ frequency. Anything faster than that may not work. For low speed pulse counting, that can be useful. I could understand that wrong. Anyone could actually go to Maxim web site and open a support case to verify that with Maxim support engineers.
Here is a question for everyone, if you have to use accurate counters to count, how many of them do you have to use in one design? I understand you may want to count many different things. Just wondering would be one, or two, or three that is enough for your purpose? We will not be able to make any change to WC8 or WC32 design. But we could make another board to fit your needs. Also possible, please let us know your pulse frequency range.