There are two white keyboard plugs below the CPU. In the picture we see see wires from the left keyboard plug to Pin 2 and Pin 4 of the MC14503B. We also see a 10K Resistor array right above keyboard plug.
So your schematic of the keyboard seems to be ok for R20 and U14.
What we don't see is the glue logic for the disable pins of U14.
From the website http://slowcomputing.org/ssouth/mc10/ we get the information
The MC-10's forty-eight key, calculator-style keyboard connects to the mainboard through two, eight-conductor ribbon cables. Keyboard status can be obtained by reading from $BFFF in memory -- I'll post more information here soon.
So the disable pins of U14 seems to be decoded to address $BFFF. When low, the inputs of U14 are switched to the data bus (D0-D5) and the CPU can read the selected row of the keyboard.
So the signals KR0 to KR7 must be outputs to select a keyboard row. If P1 is not configured as output, then maybe the KR signals are connected anywhere else? From the mainboard photo I can't see, where the right keyboard plug is connected to.