Sounds pretty normal to me. If your readout is activated by some clock edges (as it is with PS/2 AFAIR), the edges should appear only when the data values are already stabilized.
If you shift data line from 0 to 1 and send clock pulse at the same moment, you never know if the microcontroller will read the 0 (clock signal arrived first) or 1 (data was first or readout delayed). So wise keyboard manufacturers decided they first set the data line to the desired state, leave it for a short while like that so all the electronics can read its right value, then they send the clock edge which activates readout - which reads the state of the data lines.