In any system, if a signal is synchronized to a clock, then it will be considered for all the timing calculations like setup time, hold time, skew and so on. So, you would know if there are any timing violations. If the pins Sync mode is transparent, then the signal will be treated as asynchronous till it gets synced to any other clock later inside the system.
I did not see any ports in PSOC 4 M that does not having input sync. Can you tell me which port does not have this feature?
In Application Note, AN86439 - PSoC 4 - Using GPIO Pins, a note on page 33 says that Port4 and higher cannot be synchronized.
Does this mean that if I read the pin after sufficient delay then I would read the correct value ie either high or low?
Synchronization is needed for signal paths to be processed at the right time avoiding glitches. Because reading with a Pin_Read() is asynchronous in nature, no sync sampling is needed. The same applies to Pin_Write(). This will explain why neither sync nor double sync is provided for pins of ports >= 4.